Functional MRI

Functional magnetic resonance imaging (fMRI) is a MRI procedure that measures brain activity by detecting associated changes in blood flow. The primary form of fMRI uses the blood-oxygen-level-dependent (BOLD) contrast.
This is a type of specialized brain scan used to map neural activity in brain by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells.
It is non invasive, does not require to ingest substances or be exposed to radiation. The procedure is similar to MRI but uses the change in magnetization between oxygen-rich and oxygen-poor blood as its basic measure. The resulting brain activation can be presented graphically by color-coding the strength of activation across the brain or the specific region studied.
FMRI is used both in the research world, and to a lesser extent, in the clinical world.
Brain activity mapping enables revealing of the areas of neuronal activation in response to tests, motor, sensor, and other stimuli. Until recently, similar mapping was performed with the help of radionuclide methods: PET and SPECT imaging.
Functional MRI (fMRI) is based on increase of brain haemodynamics in response to cortical neuronal activity due to certain stimulus (Ramsey 2002; Pouratian et al. 2003; Sunaert 2006).
BOLD EPI-GRE registers hyperintense MR signal from active areas of the brain cortex. The registration time of one MR image is about 100 ms. fMRI signal intensity, registered by physiological load, is compared with the intensity, registered in the event of its lack. During MRI examination, the stimulation periods (duration of 30 s) alternate with control periods

fMRI neuronal activity maps of cortical motor center activation in a patient with intrinsic tumour of the paracentral area, imposed on a T1 image

(without stimulation) of the same duration. The total number of scans registered during the examination reaches 20,000. This method of stimulus presenting is called a block paradigm. The areas of statistically significant MR signal increasing during activation, revealed in the course of subsequent mathematical processing of images, correspond to areas of neuronal activity. They are marked with colour—this way the neuronal activity maps are built and these maps are imposed on T1 MRI sequences. Map construction methods subtract images obtained during neuron stimulation from control images obtained in the absence of stimulation. The subtracted image is imposed on a control scan according to its location, and areas of increased neuronal activity are marked with colour. The revealed functionally significant areas could be “imposed” on a T1 MRI sequence of the same section or on a three-dimensional (3D) brain model, and thus it is possible to estimate the ratio between the affected area (tumour) and functionally active brain areas, for example, motor, sensory or visual cortex.

Clinical Application of fMRI

Neuronal activity mapping enables planning the surgical approach and studying of the pathophysiological processes in brain. This method is used in neurosurgery in studying cognitive functions. Its perspective is in revealing the epileptic foci. Currently, fMRI is an integral part of MRI protocol in patients with brain tumours located close to the functionally important brain areas. In the majority of cases, the examination results adequately reflect the location of sensomotor, speech and acoustical areas of brain cortex.
In cases in which fMRI can locate active cortical areas, in 87% of cases there is a correspondence with the results of intraoperational electrophysiological methods, within 1-cm limits, and in 13% of cases, within 2 cm. This is evidence of the high accuracy of the fMRI technique (Nennig et al. 2007).
Performing fMRI (currently it is conducted for somatosensory and visual cortices) and tractography with mapping of the functionally active cortical areas, pyramidal or optic tracts.
Imposition of these maps over 3D brain images is promising within the framework of one MRI examination for patients with brain tumours. Based on these data, neurosurgeons plan the interventional approach and estimate the volume of neoplasm resection, and radiologists assess the areas of radiation and its distribution in tumour.

Reference : V. N. Kornienko · I. N. Pronin, Diagnostic Neuroradiology.

Vascular territories of Brain stem and Infarct correlation

The arteries of the brain stem form four groups of penetrating parenchymal vessels; the anteromedial, anterolateral, lateral and posterior arterial groups.
Each group irrigates the corresponding anteromedial, anterolateral, lateral or posterior territory within the substance of the brain stem.

There are two possible systems of nomenclature.
1 . Foix and Hillemand Classification 

The penetrating branches arising from the surface vessels are divided into PM (paramedian), SC (short circumferential), and LC (long circumferential) vessels.

2.  Gillilan and Lazorthes et al. Classification

AM (anteromedial)
AL (anterolateral)
L (lateral) and
P (posterior) group.

Reference : Duvernoy’s Atlas of the Human Brain Stem and Cerebellum

Examples: 

Ax T2wi, Left side Medullary Infarction, Vascular territory : Antero Medial group / Para Median branches.

Ax FLAIR, Left side Medial Medullary Infarction, Vascular territory : Antero Lateral group / Short circumferential branches.

Ax T2wi, Left side medullary infarction, Vascular territory : Lateral group / Short circumferential branches.

Ax T2wi, Left side medullary infarction, Vascular territory : Posterior group / Long circumferential branches.

Ax T2wi, Midline medullary infarction, Vascular territory : Bilateral Antero Medial group / Para median branches.

Ax T2wi, Pontine infarction on left side, Vascular territory : Antero Medial group / Para median branches.

Ax T2wi, Pontine infarction on left side, Vascular territory : Antero Lateral group / Short circumferential branches.

Ax T2wi, Pontine infarction, Vascular territory : Bilateral Antero Medial group / Para median branches.

Ax T2wi, Pontine infarction, Vascular territory : Antero Lateral group / Short circumferential branches.

Ax T2wi, Pontine infarction and adjacent cerebellar infarct, Vascular territory : Posterior group / Long circumferential branches.

Ax T2wi, Mid brain infarction, Vascular territory : Antero Medial group / Para median branches.

Ax T2wi, Infarction involving mesencephalic mid brain, Vascular territory : Bilateral Antero Medial group / Para median branches.

Ax Diffusion, Recent Mid brain infarction, Vascular territory : Antero Lateral group / Short circumferential branches.

Nodular calcification Spinal cord

A 35 yo female with right upper limb tingling numbness.

Findings:
Sagittal T2 and T1w images show an abnormal intra medullary low signal intensity nodular calcification at the level of C3 vertebral body, in right half of cord on axial T2w MR images, better seen on non contrast CT section. Lesion is non enhancing on post contrast sagittal Fat sag T1 and axial T1 section , appears to be a benign lesion and needs follow up imaging. Clinically appears to be significant for patients right sided tingling numbness. 

Baastrup’s Disease : Interspinous Odema / Neo-arthrosis

Sagittal T1 T2 and STIR images of lumbar region spine shows:
Degenerative changes marked at L4-5 with reduced height of disc and degenerative intra discal vacume phenomenon. An abnormal linear hyper intensity of an inter spinous odema noted at the same level. 

Baastrup’s Disease

Syn: Kissing Spines Disease, intraspinous odema, intraspinous neo-arthrosis.

Baastrup’s Disease is a type of pseudo / neo-arthrosis between adjacent spinous processes.
Common in lumbar region at L4-5.

Extreme forward flexion may result in supraspinous and intraspinous ligaments sprain with development of a spur. Repeated extension interferes with the healing. An interspinous bursae may develop due to an associated supraspinous ligament laxity and intraspinous ligament breakdown. The interspinous ligament degenerates with aging resulting in the formation of a cavity, the adjacent spinous processes keep coming in contact with each other during extension and result in formation of a joint which precede pain.
Risk Factors are degenerative disc disease, Athletics, Hyper lordosis, Paraspinal muscle atrophy, Pars interarticularis defect.
Clinically characterized by localized interspinous or spinous process pain without a referral pattern, pain present for many years with progressive worsening over time.

Imaging: 
Lateral view LS spine radiograph may demonstrate sclerotic changes or flattening of adjacent spinous processes.
MRI sagittal T2 and STIR images are needed assess interspinous edema.
Bone scan with SPECT can detect increased osteoblastic activity that is associated with reactive sclerosis.

Treatment: Bed rest in semi upright sitting position, Surgical cavity resection, Surgical fusion.

References:
Haig AJ, Harris A, Quint DJ. Baastrup’s disease correlating with diffuse lumbar paraspinal atrophy: a case report. Arch Phys Med Rehabil. 2001 Feb;82(2):250-2.
Mitra R, Ghazi U, Kirpalani D, Cheng I. Interspinous ligament steroid injections for the management of Baastrup’s disease: a case report. Arch Phys Med Rehabil. 2007 Oct;88(10):1353-6.
Panagos A. Rehabilitation Medicine Quick Reference-Spine (ed. Buschbacher R.M.) New York: Demos Publishing; 2010. p. 20-21.

Unidentified bright objects (UBO) of NF1

A 09 yo male complaining of generalized tonic-clonic seizures since 2years.
Neurological examination normal.
General examination revealed multiple cafe-au-lait spots and axillary freckling.

MRI brain shows faint T2 hyper intensities in left basal ganglion, tectum of mid brain and right half of Pons non enhancing on post contrast, suggestive of unidentified bright objects (UBO) of NF1. 

UBOs are 'T2 hyper intense foci' or focal areas of high signal intensity (FASI), seen in 60-80 percent of patients with Neurofibromatosis Type I (NF1). These lesions typically appear around 3 yr, increase in number and size until 10-12 yr, and then decrease or even disappear. Common locations include basal ganglia, thalami, dentate nucleus of cerebellum and brainstem. Pathologically, these lesions correspond to vacuolar changes in the myelin sheath.
Even though these lesions generally do not cause neurological symptoms they have been correlated with learning disabilities.
A study conducted on 100 has revealed a strong relationship between cognitive and behavioural problems with these focal areas of high signal intensity (FASI or UBO) in children with NF1. The long term effects of these hyper intensities not yet documented.

Reference : NEUROFIBROMATOSIS TYPE I: NEUROPSYCHOLOGY AND MRI CORRELATES, R Feldmann. M Oelerich, T Allkemper, U Wiegard, M Pietsch, J Weglage

Department of Pediatrics, and Department of Radiology, University of Münster, Germany.

ICA Aneurysm

Sellar meningioma

A young female with visual deficit, previous CT report mentions a sellar supra sellar iso dense enhancing mass. Possibility given was Macro adenoma.

Pt refereed for further evaluation by MRI.

Sagittal T2w images show a sellar supra sellar soft tissue signal intensity well circumscribed mass.Pituitary seen separately in at the floor of hypophyseal fossa. Lesion show homogenous enhancement, a focal dural tailing anteriorly on sagittal post contrast T1 w images.

Radiological diagnosis: Sellar meningioma.

Take home massage is all sellar supra sellar masses are not macro adenoma or Craniopharyngioma. Never play on front foot while reporting CT. Always entertain DDs for sellar supra sellar masses on CT and advise MRI for further evaluation as MRI can demonstrate sellar anatomy better than CT due to its high resolution and multi planner imaging capability compared to CT. MRI can demonstrate pituitary separately in hypophyseal fossa which rules out Macroadenoma as in this case of sellar supra sellar meningioma.

Hemangioblastoma MRI

A 50 yo female with headache and giddiness.

Findings:

Axial T2w image show a mixed signal intensity posterior fossa mass with cystic as well as solid component. Solid component is near tentorium intensely enhancing on post contrast T1. Flow voids in this solid component and adjacent to it is very typical of a Hemangioblastoma. 

Mass effect on medulla and Pons with obstructive hydrocephalus.

Radiological and histopathological diagnosis : Hemangioblastoma.

Hemangioblastoma

A highly vascular tumor.

An intra axial posterior fossa mass with cyst and an enhancing mural nodule is a diagnostic clue.

Currently classified as meningeal tumor of uncertain histogenesis (WHO, 2000)

Locaion:

90% posterior fossa (m/c) in that 80% cerebellar hemispheres, 15% Vermis, 5% in other places  fourth ventricle, medulla.

10% Supratentorium.

In ~ 60% of cases mass present as cyst + mural nodule and in ~ 40% of cases only as a solid nodule.

Imaging:

Cyst is clear, density on CT and signal intensity on MRI same as that of Csf, non enhancing thin imperceptible wall.

Mural nodule on CT may be iso to hyper dense, intense and homogenous enhancement. On MRI hypo to iso intense on T1, hyperintense on T2 and FLAIR. May see flow voids within the nodule with adjacent vascular feeders on T2w images, intense and homogenous enhancement on T1 images implies to its highly vascular nature. May show low signal intensity hemosiderin staining on GRE if associated to with any bleed.

Presentation is usually with headache, dysequilibrium, dizziness may be due to its mass effect and hydrocephalus.

Age : for sporadic: 40-60 yr and for familial : can occur at younger age. Slight male predominance.

Closest DD is Pilocytic Astrocytoma; mural nodule show mild to moderate enhancement not this intense, not characterized by flow voids and feeders. Seen in relatively younger age group.

Similar case:

http://www.neuroradiologycases.com/2012/11/hemangioblastoma.html

Hirayama Disease MRI

An 18 yo male with 4 year history of slowly progressive weakness of forearms and hand marked on right side. Neurologic examination revealed atrophic changes in thenar, hypothenar muscles, interossei of the hands, muscles of forearm more on right side. Deep tendon reflexes symmetrically normal. No Babinski sign. Normal pin-prick, vibration and joint position sensation. No extra pyramidal signs.

Previous MRI cervical spine report at other center mentions spinal cord atrophy in lower cervical region. Rest of the spine and spinal cord screening unremarkable.

We performed MRI Cervical spine, sagittal T2w MR images revealed cord atrophy at the C5-6 disc level, a linear signal abnormality in anterior half of cord. The atrophy marked in anterior half of cord, signal abnormality confined to anterior half of cord in the region of either side anterior horn cells marked on right side confirmed on Axial T2w images. Study repeated during flexion with clinical suspicion of Hirayama disease shows marked anterior displacement of the posterior wall of dura with marked flattening of the cord. Flow void noted in this posterior epidural space appears to be the engorged venous plexus due to dural shifting. Clinical presentation and flexion MR imaging findings led to the diagnosis of Hirayama disease. Neck collar was advised to prevent neck flexion and to prevent further progression of disease and disease symptoms with follow up MRI Imaging.

Discussion

Hirayama et al first reported this disease in 1959.

Hirayama disease, a non progressive juvenile spinal muscular atrophy, occurs mainly in young males between the ages of 15 and 25 years. The clinical features include insidious onset, predominantly unilateral upper extremity weakness and atrophy, cold paresis, and no sensory or pyramidal tract involvement.

Pathologic studies have shown the lesions only in the anterior horns of the spinal cord from C-5 to T-1, particularly marked at C-7 and C-8.

Current neuroradiologic techniques have shown forward displacement of the posterior wall of the lower cervical dural canal in neck flexion, which is presumed to be a primary

pathogenetic mechanism of Hirayama disease. The mechanism of this anteriorly displaced dural canal has been explained by Kikuchi et al as a tight dural canal in flexion,

caused by a disproportional length between the vertebrae and the dural canal.

Early diagnosis of disease is necessary, because placement of a cervical collar will prevent neck flexion, which has been shown to stop disease progression. Atrophy on routine nonflexion MR studies especially at the lower cervical cord, should raise the suspicion of Hirayama disease. When this sign is seen, a flexion MR study should be performed to confirm the diagnosis.

Similar case:
http://www.neuroradiologycases.com/2011/08/hirayama-disease.html

Reference : Hirayama Disease: MR Diagnosis, Chi-Jen Chen, Chiung-Mei Chen, Chia-Lun Wu, Long-Sun Ro, Sien-Tsong Chen, and Tsong-Hai Lee, AJNR Am J Neuroradiol 19:365–368, February 1998 

Fatty filum terminale MRI

Syn: Lipoma of the filum terminale, filar lipoma.
A relatively common benign finding on MR imaging of the lumbar spine, seen in ~ 5 % of cases.

On MRI the abnormality typically is thin and linear, extends over only few segments. Signal iso intense to fat on all pulse sequences may show chemical shift artefact on T2* GRE sequences. T1 and T2 hyperintens with signal supression on STIR.

In most cases is an incidental finding of no clinical significance. However it is considered as one of the causes in tethered cord syndrome and may be associated with tethered cord, where there is associated markedly thickened filum with low lying conus. Location and the size of fatty filum are considered as the important factors for Tethered cord syndrome. The thickened fatty filum terminale (more than 2mm) considered as one of the causes of the tethering. Fat in the filum may represent mesodermal cells that did not properly migrate to their normal position in the process of canalization. The presence of fatty tissue may alter the developmental properties of the filum and may predispose patients to cord tethering. Bursara et al. reported the correlation between the fat and the neural dysfunctions with MRI. They concluded that fat in the filum terminale within 13mm of the conus medullaris was most predictive of neurological deficits. And TCS in adults is caused by the anoxia due to over-stretching of the conus medullaris - See more at h:ttp://www.ispub.com/journal/the-internet-journal-of-spine-surgery/volume-3-number-1/fatty-filum-terminale-on-mri.html#sthash.5KQVStuW.dpuf

In asymptomatic patients, nothing need be done. Difficulty arises in patients who have some symptoms suggesting tethered cord syndrome, but whose conus terminates at a normal level. Controversy as to the benefits of division of a fatty filum in such patients exists.

Imagingwise there is little or no differential when signals of fat is confirmed, however other filum terminale lesions like paraganglioma of the filum terminale and myxopapillary ependymoma can be considered.

Dural AV fistula

Plain CT and MR Axial T2w images show abnormal serpigenous vascular hyper density on CT and T2 flow voids on MRI marked in posterior fossa at the floor and along tentorial dura suggestive of dural AV fistula.
An associated abnormal dilatation of petrosal sinuses noted on MR Angio.

Dural arteriovenous fistula (DAVF)

Dural AVF, a rare, abnormal connectivity between arteries and veins, lies exclusively along dural covering of the brain or spinal cord, and referred accordingly as a cranial DAVF and spinal DAVF.
Cranial DAVF is supplied by branches of the carotid artery (external and internal carotid arteries) and possibly also by branches of the vertebral artery before these arteries penetrate the dura.
The fistula communications seen as serpigenous dilated vessels with T2 flow voids along dura overlying cererebral convexity and along tentorium. Frequently the blood flow in a DAVF is very high, and it may cause blood to flow in the opposite direction of normal over the brain's surface.

Commonly diagnosed in women over the age of 40 years. Unlike AVMs, which are thought to be present from birth, cranial DAVF most often develop later in life following hypoplasia or thrombosis of dural venous sinus particularly superior sagittal sinus.

Cranial DAVF may present with pulsatile tinnitus or pulsatile proptosis, impairment of vision and eye movement, isolated but persistent or progressive headache; hemorrhage
Unfortunately, the diagnosis may be missed or delayed because such lesions occur so rarely, CT may be normal and even in case of MRI, a common practise of inadequate sequences particularly screening protocols used for brain and spine.

Pathogenesis of Dural AV fistula:
Dural AV fistula are shunts between the meningeal arterial networks and the dural venous sinuses. Long standing dural sinus thrombosis result in obstruction in venous outflow which raises intra cranial venous sinus pressure. This venous hypertension leads to ischemia, followed by aberrant angiogenic activity along the Dura. CVT here is the primary event that result in venous hypertension and fistula. Sinus thrombosis may be the primary even as result of turbulent flow in the Dural venous sinus secondary to DAVFs.

Treatment:
Highly challenging, various line of management and materials are under debates.
Intra sinus stenting can relieve raised venous sinus pressure but may increase arteriovenous pressure gradient and shunt flow.
Arterial embolization of DAVF, without correction of venous hypertension can give rise to another fistula.
Intermittent carotid arterial compression.
Percutaneous intra arterial embolization using detachable balloons, isobutylcyanoacrylate, or polyvinyl alcohol particles.
Transvenous embolization with coils or liquid adhesives.
Surgical venous bypass using saphenous vein.
Gamma knife stereotactic surgery.

Similar Case: http://www.neuroradiologycases.com/2011/09/dural-arteriovenous-fistula-davf.html

Spinal cord ischemia in a case of Aortic Dissection

A young male admitted with sudden onset both lower limb weakness with an associated severe backache. Motor loss more than sensory. Advised MRI whole spine screening for spinal cord. 

Day 1 MRI

Findings:

Sagittal T2w images of spine show faint abnormal intramedullary T2 hyper intensity confined to anterior cord in dorsal region.

Day 2 MRI with axial T2

Sagittal T2w image of cervico dorsal region spine with axial T2w images at the level of signal abnormality of spinal cord show same abnormal intramedullary T2 hyper intensity confined to anterior half of cord in dorsal region becoming more obvious on this follow up MRI.

Radio logical diagnosis: Acute Spinal cord Ischemia.
Further evaluation revealed an thoraco abdominal Aortic Dissection on CT Angiography. 


Discussion:

The differential diagnosis of acute onset paraplegia includes spinal cord injury, tumor, infection, Disc herniation, Demyelination or aortic dissection - occlusion. Aortic dissection in acute paraplegia is missed in up to 50% of cases.
Aortic dissection is uncommon, accounts for approximately 1 in 10,000 hospital admissions. The mortality rate is as high as 80% without aggressive treatment. Clinical presentation is commonly a severe painful tearing sensation usually located interscapular or mid-back area. Other common signs and symptoms include cardiovascular collapse, acute myocardial infarction, oliguria, syncope and cold extremities.

Classification of aortic dissection; DeBakey classification divides dissections into 3 types. Type I involves the ascending aorta, aortic arch and descending aorta. Type II involves only the ascending aorta. Type III involves the descending aorta distal to the left subclavian artery.
Stanford classification Type A includes involvement of the ascending aorta and Type B excludes it.

Neurologic sequelae of aortic dissection occur in ~ one third of cases. These sequelae fall into 3 categories: cerebral ischemia, spinal cord ischemia and ischemic peripheral neuropathy.
When the ascending aorta is involved, cerebral ischemia may result, present as a stroke or encephalopathy. Paraplegia with or without sensory loss is a rare phenomenon, occurs in about 2% to 8% of patients, results from dissection of the descending aorta. The clinical picture of motor loss without complete loss of sensation is known as anterior artery syndrome. Painful peripheral neuropathy result when the iliac arteries are involved.

The artery of Adamkiewicz arises from the posterior aspect of the aorta and supplies the anterior aspect of the major portion of spinal cord. This artery is can be involved in the aortic dissection. When involves most areas of the spinal cord receive additional blood flow from the collateral flow. In the thoracic spinal cord, there is a “watershed” area which is especially prone to ischemia.

Conclusion: Acute aortic dissection to be considered in the differential diagnosis of acute onset paraplegia. 

Cavernoma with Bleed

Non contrast CT study of brain shows right frontal Cavernoma with punctate calcifications. An adjacent Gliosis noted. 
MRI study of brain shows right frontal Cavernoma appears to be complicated with bleed which has resolved and is evident by Gliosis with low signal intensity hemosiderin staining on GRE. It is not uncommon for a Cavernoma patient to be asymptomatic, massive bleed in a Cavernoma is known but a rare complication. 


Cavernoma (Cavernous Malformation)
A benign vascular hamartoma, composed of closely packed immature blood vessels with intra lesional micro hemorrhages, without any neuronal tissue.
Best diagnostic clue is "Pop corn ball" like appearance with hemosiderin rim on T2w images.
Occur anywhere in brain. Rare in Spinal cord.
Vary in size from few mms to cms. Average size is between 1 to 5cm.
Usually single solitary, may be multiple, discrete lesions.
MRI is more sensitive and specific for detection of lesion.
Hyper dense on non contrast CT. Punctate Calcifications seen in ~ 50% cases. No to faint enhancement on post contrast.
On MRI lobulated appearance due to multiple locules which show variable signals, depending up on the blood degradation products. T1 bright locules attributed to Meth Hb - a sub acute stage blood degradation product. Low signal intensity hemosiderin rim on T2 images. Low signal intensity blooming on  T2*GRE images. No to faint enhancement on post contrast T1 images.
No to mild peri lesional odema.
No mass effect.

Clinical presentation:
Seizures 50%
Neuro deficit 25%
Asymptomatic 20%, detected as an incidnetal finding.
No intervention is a rule. But need follow up imaging as it may show progression or regression in size. Rarely show massive bleed.
Can affect any age group.
No gender preponderance.
Familial association in Hispanic Americans - Multiple Cavernoma Syndrome, carries higher risk for bleed and re bleed.

Similar cases:
cavernoma
cavernous-malformation
venous angioma with bleed

Multiple Brain and a Spinal Cavernous Malformation in same patient

A 40 yo male presented with sudden onset paraplegia. 

MRI Spine done first revealed an intra medullary focal lesion with T1 bright meth Hb staining and low signal intensity hemosiderin staining on GRE. 

Brain screening done in same setting revealed multiple similar intra cranial lesions. 

MRI brain and spine images of same patient.

Description of findings:
MRI Brain shows multiple intra axial focal lesions with typical pop corn ball appearance on T2w images with low signal intensity hemosiderin rim. Few T1 bright locules of meth Hb - a sub acute stage blood degradation product. Lesion show low signal intensity blooming on T2*GRE. No mass effect.
MRI Spine shows a similar intra medullary focal lesion at the level of C7, marked adjacent cord odema.

Diagnosis: Multiple Brain and a Spinal Cavernous Malformation.

Cavernoma (Cavernous Malformation)

A benign vascular hamartoma, composed of closely packed immature blood vessels with intra lesional micro hemorrhages, without any neuronal tissue.
Best diagnostic clue is "Pop corn ball" like appearance with hemosiderin rim on T2w images.
Occur anywhere in brain. Rare in Spinal cord.
Vary in size from few mms to cms. Average size is between 1 to 5cm.
Usually single solitary, may be multiple, discrete lesions.
MRI is more sensitive and specific for detection of lesion.
Hyper dense on non contrast CT. Calcification seen in ~ 50% cases. No to faint enhancement on post contrast.
On MRI lobulated appearance due to multiple locules which show variable signals, depending up on the blood degradation products. T1 bright locules attributed to Meth Hb - a sub acute stage blood degradation product. Low signal intensity hemosiderin rim on T2 images. Low signal intensity blooming on  T2*GRE images. No to faint enhancement on post contrast T1 images.
No to mild peri lesional odema.
No mass effect.

Clinical presentation:
Seizures 50%
Neuro deficit 25%
Asymptomatic 20%, detected as an incidnetal finding.
No intervention is a rule. But need follow up imaging as it may show progression or regression in size. Rarely show massive bleed.
Can affect any age group.
No gender preponderance.
Familial association in Hispanic Americans - Multiple Cavernoma Syndrome, carries higher risk for bleed and re bleed.

Similar cases: 

Cavernoma

cavernoma-with-bleed

Intraventricular-cavernoma

venous angioma with bleed

Antiphospholipid Antibody Syndrome MR Angio Brain

A 30 yo female with migraine like symptoms. Not responding to treatment. 

Findings:
3 D TOF Non contrast MR Angiography of Brain shows sparsity of cortical branches of left MCA compared to left.
2 D TOF Non contrast MR Angiography of Neck normal.
Brain FLAIR and Diffusion images unremarkable apart from few ischemic lesions in left parietal peri ventricular white matter.

Further evaluation : positive for Antiphospholipid Antibody. 

Antiphospholipid antibody syndrome

Syn: Antiphospholipid syndrome, APS, APLS, Hughes syndrome.
An autoimmune, hypercoagulable state caused by antibodies against cell-membrane phospholipids that provokes blood clots (thrombosis) in both arteries and veins as well as pregnancy-related complications such as miscarriage, stillbirth, preterm delivery, or severe preeclampsia. There are also associations between antiphospholipid antibodies and headaches, migraines, and oscillopsia. Some studies have shown the presence of antiphospholipid antibodies in the blood and spinal fluid of patients with psychological symptoms.
There is autoimmune production of antibodies against phospholipid (aPL), a cell membrane substance cardiolipin (anti-cardiolipin antibodies) and β2 glycoprotein I.
The term "primary antiphospholipid syndrome" is used when APS occurs in the absence of any other related disease.
APS however also occurs in the context of other autoimmune diseases, such as systemic lupus erythematosus (SLE), in which case the term "secondary antiphospholipid syndrome" is used.
In rare cases, APS leads to rapid organ failure due to generalised thrombosis; this is termed "catastrophic antiphospholipid syndrome" (CAPS) and is associated with a high risk of death.
Antiphospholipid syndrome is diagnosed with blood tests.
Requires treatment with anticoagulant medication such as heparin to reduce the risk of further episodes of thrombosis and improve the prognosis of pregnancy. Warfarin/Coumadin is not used during pregnancy because it can cross the placenta, unlike heparin, and is teratogenic.

Persistent Trigeminal artery MR Angio

Arterial communications between the carotid and vertebrobasilar systems in the fetus may occasionally persist in the adult.
A primitive trigeminal artery is the most cephalad and common of these persistent fetal anastomoses.
Arises from the presellar ICA extends posteriorly to join basilar artery usually between the origins of the superior and anterior inferior cerebellar arteries. The anomalous vessel usually has a parasellar course.
Direction of flow in the artery is usually from the ICA to the basilar.
Discovered incidentally.
Coexisting other intracranial vascular abnormalities in ~ 25% of patients are intracranial aneurysms, arteriovenous malformations, carotid-cavernous fistulae, and moyamoya.

'The tau sign' the configuration resembling the Greek letter 'T' formed by the joining of the proximal portion of the trigeminal artery to presellar portion of ICA as it turns from a vertical to a horizontal course

In this case an associated hypo plastic basilar noted.

Hemangioblastoma MRI

Axial T2w image show a cystic posterior fossa mass with an intense homogeneously enhancing eccentric mural nodule near right sigmoid sulcus.

Radiological and histopathological diagnosis : Hemangioblastoma.

Hemangioblastoma
A highly vascular tumor.
An intra axial posterior fossa mass with cyst and an enhancing mural nodule is a diagnostic clue.
Currently classified as meningeal tumor of uncertain histogenesis (WHO, 2000)
Locaion:
90% posterior fossa (m/c) in that 80% cerebellar hemispheres, 15% Vermis, 5% in other places  fourth ventricle, medulla.
10% Supratentorium.
In ~ 60% of cases mass present as cyst + mural nodule and in ~ 40% of cases only as a solid nodule.
Imaging:
Cyst is clear, density on CT and signal intensity on MRI same as that of Csf, non enhancing thin imperceptible wall.
Mural nodule on CT may be iso to hyper dense, intense and homogenous enhancement. On MRI hypo to iso intense on T1, hyperintense on T2 and FLAIR. May see flow voids within the nodule with adjacent vascular feeders on T2w images, intense and homogenous enhancement on T1 images implies to its highly vascular nature. May show low signal intensity hemosiderin staining on GRE if associated to with any bleed.

Presentation is usually with headache, dysequilibrium, dizziness may be due to its mass effect and hydrocephalus.
Age : for sporadic: 40-60 yr and for familial : can occur at younger age. Slight male predominance.

Closest DD is Pilocytic Astrocytoma; mural nodule show mild to moderate enhancement not this intense and homogeneous, not characterized by flow voids and feeders. Seen in relatively younger age group.

Similar case:
http://www.neuroradiologycases.com/2012/11/hemangioblastoma-mri.html

Ulnar Nerve Abscess – Leprosy

A 40 year known HIV positive female presented with diffuse swelling of left arm around elbow painful for last 15 days, it was initially pain less with an associated numbness of little finger since 6 months, numbness and swelling was increasing gradually. On examination a nodular swelling behind the elbow on the medial aspect with tenderness. Limited elbow extension. No any skin discoloration. 

MRI elbow joint advised with preference to ulnar nerve. 

MRI shows marked focal nodular enlargement of ulnar nerve at elbow joint, thickening of rest of the ulnar nerve with marked inflammation on STIR sequence in an adjacent muscle compartments and facial planes. 

Imaging wise possibility of Ulnar neuritis / Abscess was given and advised to rule out Leprosy clinically. 

Incision and drainage of the abscess done followed by culture and sensitivity test. Histopathology report mentions caseating epitheloid granuloma and giant cells. Disrupted native nerve fibers within and around the granuloma. Acid fast bacilli in singles and clusters consistent with tuberculoid Hansen’s disease.

Imaging and histopathological diagnosis : Ulnar nerve Abscess – Leprosy. 

Discussion: 

Leprosy is a chronic granulomatous infection, caused by mycobacterium leprae.

Primarily affecting the peripheral nerve trunks and cutaneous nerves.

Classically presents with neural or dermal signs and symptoms. 

Ulnar nerve is most commonly involved in fact Leprosy is the only disease in which abscess develop in nerve trunk. These abscesses are usually chronic cold abscess. 

Leprosy has a high prevalence in India of about 5 per 10000 populations with about 70% of globally recorded cases. The leprosy bacilli have a characteristic feature of nerve involvement, involvement of testis, lymph nodes, spleen, liver, larynx, bone marrow.

Contribution of imaging is limited in leprosy but reorganization of the condition is important by radiologist as management is different as clinically and imaging wise other dd often include nerve sheath tumor. 

Broadly there are three types of leprosy, the tuberculoid, lepromatous and borderline. The differentiation is based on symptoms, bacterial load and individual’s immune response.

In Tuberculoid leprosy the primarily affected nerves are pressure/trauma dependent  The most commonly involved nerve is ulnar nerve followed by median nerve, sural nerve, radial and branches of facial nerve.

In lepromatous leprosy the nerve damage is widespread and symmetrical with extensive intracutaneous nerve involvement and resembles symmetric polyneuropathy. Sensory loss occurs in the coolest areas of body like dorsum of hand and feet, ear, dorsum of fore arm and anterolateral parts of leg.

Borderline leprosy has characteristic of both tuberculoid and lepromatous.

Management is often surgical after failure of steroid treatment and that is Epineurotomy by multiple longitudinal incisions and external decompression to relive the internal pressure through out the involved segment. 

Neurocysticercosis starry sky appearance

Multiple round cystic focal lesions with an eccentric scolex typical of Neurocysticercosis.
Lesions of various stages noted.
Few of them show mild perilesional odema on FLAIR, punctate low signal intensity of calcification of scolex on GRE and thin ring enhancement on post contrast T1. 

Neurocysticercosis (NCC) 


Intracranial parasitic infection caused by the pork tapeworm, Taenia solium.
Four pathologic stages: Vesicular, colloidal vesicular, granular nodular, nodular calcified.

Diagnostic clue is Cyst with "dot" inside.
Most common location is convexity subarachnoid spaces. May involve cisterns> parenchyma> ventricles. Basal cistern cysts may be racemose (grape-like). Parenchymal cysts often hemispheric, at gray-white junction. Intraventricular cysts are often isolated. Fourth ventricle is most common intra ventricular location. Rare locations are Sella, orbit, spinal cord.

Size of Cysts variable, typically 1 cm, range from 5-20 mm and contain a scolex; scolex 1-4 mm. Subarachnoid cysts may be larger, up to 9 cm reported. Cysts are often rounded or ovoid cyst, solitary in 20-50%. When multiple, usually small number of cysts, disseminated form ("miliary" NCe) is rare.

Imaging varies with developmental stage of cyst and host immune response. Lesions may be at different stages in same patient.
MR Findings
• TlWI
o Vesicular stage: Cystic lesion isointense to CSF. May see discrete, eccentric scolex (hyperintense)
o Colloidal vesicular stage: Cyst is mildly hyperintense to CSF.
o Granular nodular stage: Thickened, retracted cyst wall; edema decreases.
o Nodular calcified stage: Shrunken, Ca++ lesion.
o Useful to detect intraventricular cysts.
• T2WI
o Vesicular stage: Cystic lesion isointense to CSF. May see discrete, eccentric scolex. No surrounding edema.
o Colloidal vesicular stage: Cyst is hyperintense to CSF. Surrounding edema, mild to marked.
o Granular nodular stage: Thickened, retracted cyst wall; edema decreases
o Nodular calcified stage: Shrunken, Ca++ lesion
• FLAIR
o Vesicular stage: Cystic lesion isointense to CSF. May see discrete, eccentric scolex (hyperintense to
CSF); no edema.
o Colloidal vesicular stage: Cyst is hyperintense to CSF. Surrounding edema, mild to marked. Useful to detect intraventricular cysts (hyperintense).
• T2* GRE: Useful to demonstrate calcified scolex.
• DWI: Cystic lesion typically isointense to CSF
• TI C+
o Vesicular stage: No enhancement typical, may see mild enhancement.  May see discrete, eccentric scolex enhancement.
o Colloidal vesicular stage: Thick cyst wall enhances. Enhancing marginal nodule (scolex)
o Granular nodular stage: Thickened, retracted cyst wall; may have nodular or ring-enhancement
o Nodular calcified stage: Small calcified lesion, rare minimal enhancement

In children, may see "encephalitic cysticercosis" with multiple small enhancing lesions and diffuse edema. Intraventricular cysts may cause ventriculitis and/or hydrocephalus.
Cisternal NCC may appear racemose (multilobulated, grape-like), typically lacks scolex
E/o Complications: Meningitis, hydrocephalus, vasculitis


NCC is the most common cause of acquired epilepsy in developing countries like india.
It can present variably depending on the location and stage of cysts in the nervous system and the host immune response. The most common presentation of parenchymal NCC is seizures that are usually focal and brief. Status epilepticus occurs in some cases. About a third of cases have headache and vomiting.

Although treatment with cysticidal therapy continues to be debated, there is increasing evidence that it helps through increased and faster resolution of CT lesions; whether there is any improvement in long-term seizure control needs further study. It should not be used in cysticercus encephalitis or in ophthalmic NCC and used with caution in extraparenchymal NCC. It is of no use in calcified lesions.
Corticosteroids are used simultaneously to reduce cerebral oedema.
Seizures respond well to a single antiepileptic, and the seizure recurrence rate is low in cases with single lesions. Those with multiple, persistent or calcified lesions usually have recurrent seizures.
Extraparenchymal NCC is often associated with intracranial hypertension, hydrocephalous and chronic meningitis; it has a guarded prognosis; surgical intervention is required in many cases.
Management of NCC needs to be individualized. NCC is potentially eradicable; proper sanitation, hygiene and animal husbandry are warranted.

Holoprocencephaly

Holoprocencephaly with an associated fused metopic suture /single frontal "plate" of bone. 

Formerly called arrhinencephaly. 

Best diagnostic clue is Monoventricle + fused (uncleaved) frontal lobes ~ absent anterior midline falx/fissures and Anteriorly displaced Sylvian fissures. 

Associated with Hypotelorism, fused metopic suture /single frontal "plate" of bone, Azygous / absent anterior cerebral artery (ACA) on MR Angio.

Metopic Synostosis

'Trigonocephaly' Metopic Synostosis

Note the associated excessive convolutional marking on inner table of skull with dilated parietal emissary foramen indicating long term raised intra cranial pressure.

Craniosynostosis
Craniosynostosis (from cranio, cranium; + syn, together; + ostosis relating to bone) is a condition in which one or more of the fibroussutures in an infant skull prematurely fuses by ossification.  thereby changing the growth pattern of the skull. Because the skull cannot expand perpendicular to the fused suture, it compensates by growing more in the direction parallel to the closed sutures. Sometimes the resulting growth pattern provides the necessary space for the growing brain, but results in an abnormal head shape and abnormal facial features. In cases in which the compensation does not effectively provide enough space for the growing brain, craniosynostosis results in increased intracranial pressure leading possibly to visual impairment, sleeping impairment, eating difficulties, or an impairment of mental development combined with a significant reduction in IQ.

Craniosynostosis occurs in one in 2000 births. Craniosynostosis is part of a syndrome in 15 to 40% of the patients, but it usually occurs as an isolated condition.

Causes of premature fusion
The dura mater plays an important role in determining closure or patency of the suture.
Many things are still not understood about the suture biology and the exact causative pathways remain yet to be completely understood.
Multiple potential causes of premature suture closure have been identified, such as the several genetic mutations that are associated with syndromic craniosynostosis.The cause of nonsyndromic craniosynostosis however, is still greatly unknown. Most likely, a role is played by biomechanical factors, as well as environmental, hormonal and genetical factors.
Biomechanical factors: fetal head constraint during pregnancy.
Environmental factors : maternal smoking and the maternal exposure to amine-containing drugs likely through effects on fibroblast growth factor receptor genes.
Hormonal factors: Hyperthyroid induced craniosynostosis is a hormone mediated premature closure due to high levels of thyroid hormone.
Genetic factors : fibroblast growth factor receptor 3 (FGFR3) and TWIST genes.

Scaphocephaly
The name providing a direct hint regarding the deformity of the skull. The literal meaning of the Greek derived word ‘scaphocephaly’ is boathead. A synonymous term is 'dolichocephaly' (the prefix dolicho- means elongated).
Premature sagittal suture closure restricts growth in a perpendicular plane, thus the head will not grow sideways and remain narrow.
This is best seen in a view standing above the child looking downwards at the top of the head.
A prominent forehead, called frontal bossing, and a prominent back portion of the head, called coning. When viewed from sideways the resulting shape of the head will look a bit like a boat.

Trigonocephaly
A result from the premature closure of the metopic suture result in a narrow forehead, which is even further emphasized by ridging of the suture. The resulting shape can best be assessed from a top view again, which will reveal a somewhat triangular form of the head.
Trigonocephaly is also a Greek derived word, which can be translated as triangular shaped head. A facial feature of metopic synostosis is hypotelorism.

Plagiocephaly
The Greek word plagios means skew. Plagiocephaly can be sub classified in Anterior Plagiocephaly and Posterior Plagiocephaly.
Anterior Plagiocephaly
Anterior plagiocephaly is a clinical description of unilateral coronal synostosis. Children born with unilateral coronal synostosis develop due to compensatory mechanisms a skew head; a plagiocephaly.
The sagittal suture ‘divides’ the coronal suture in two halves; unilateral meaning that either the right side or the left side to the sagittal suture is fused. This fact immediately raises an important point. Unlike closure of the sagittal or the metopic suture, right and left are not the same in unilateral coronal synostosis. This asymmetry shows in the skull deformity, as well as in the facial deformity and the complications.
This time, the skull deformity can only partly be predicted using Virchow’s law. Growth is arrested in the plane perpendicular to the fused suture and the forehead is flattened, but only at the ipsilateral side of the head. Ipsilateral indicates the same side of the head as where the suture is closed. Compensatory growth occurs in a parallel plane, as well as in a perpendicular plane. An increase in growth at the metopic and the sagittal suture accounts for the parallel plane and will result in bulging at the temporal fossa and an increase in width of the skull. Compensatory growth in the perpendicular plane occurs on the side of the head with the patent coronal suture, the contralateral side. Half of the forehead will bulge forwards as a result.
Assessment of the skull from a top view shows asymmetry of the frontal bones, an increased width of the skull and a forward displacement of the ear at the ipsilateral side of the head.Assessment of the skull from a frontal view will show asymmetrical features of the face, including a displacement of the chin point of the jaw and a deviation of the tip of the nose.The chin point is located more to the contralateral side of the head, due to the ipsilateral forward displacement of the temporomandibular joint together with the ear.The tip of the nose will also point towards the contralateral side.Complications based on the skull deformation include malocclusion of the jaw and in as many as 90% - a subtle form of - strabismus, the last being caused by the asymmetrical placement of the orbits.
Posterior Plagiocephaly
Unilateral lambdoid synostosis is also called posterior plagiocephaly, indicating that this gives, just like unilateral coronal synostosis, a ‘skew head’. The difference is that this time, the deformity mostly shows at the occiput.
Restriction of growth will occur at the ipsilateral side of the head; compensatory growth will occur at the contralateral side of the head. This growth pattern exerts an effect at the base of the skull, which is not even when the child is assessed from a point of view standing behind the child, as well as on the cervical spine, which shows a curvature. In addition, an asymmetry of the ears can be seen, with the ear on the ipsilateral side placed further to the back. Also, again from a point of view standing behind the child, a bulging of the mastoid can be seen. Minimal forehead asymmetries are typically seen.

Brachycephaly
Brachycephaly, or a ‘short head’, is the result of a closure of both the coronal sutures result in a child’s head with a restriction of growth in the forward direction and in the backward direction; recessed frontal bones and a flattened occiput. compensatory growth will occur sideways, due to the sagittal suture, and upwards, due to the lambdoid sutures.

Oxycephaly
Oxycephaly, also known as turricephaly and high-head syndrome, is a type of cephalic disorder. This is a term sometimes used to describe the premature closure of the coronal suture plus any other suture, like the lambdoid,

Pansynostosis
The word pansynostosis is also Greek derived and can be translated as ‘all one bone’, indicating that all of the sutures are closed. The term is used to describe the children with three or more sutures closed. Pansynostosis can present in several ways. The appearance can be the same as that seen with primary microcephaly: a markedly small head, but with normal proportions.