Unilateral hemispheric odema

DDs or to be evaluated further for:
- Evolving hemispheric infarction : Effacement of hemispheric cortical sulci due to cytotoxic odema may be the only sign on initial CT studies so unilateral cerebral odema should be promptly investigated with MRI Diffusion to rule out Evolving or Hyper acute infarct. May need MR Angio and Veno accordingly.
- Post traumatic unilateral cerebral edema : Usually have an associated contusion or extra axial bleed but isolated unilateral cerebral swelling is uncommon but known. Possible when impact of injury is more on one of the hemisphere. Such pts likely to have other post traumatic micro lesions like petechial bleed or axonal shearing innury which may not be obvious on CT. May have very thin layer of subdural hematoma on the initial CT studies which may not be obvious on present CT study. May need MRI in such cases to rule out associated such post traumatic micro lesions like petechial bleed or axonal shearing injury which may not be obvious on CT.
- Peri Ictal or Post Ictal unilateral cerebral edema:  
- Unilateral hemispheric encephalitis: Rare type of encephalitis involves single hemisphere, steroid responsive. Benign course different from that of Rasmussen's Encephalitis.
- Unilateral Hyperperfusion syndrome: Rare but reported after cardiac surgeries and hepatic failures. Completely reversible with excellent outcome. Appears to be a variant of hyperperfusion syndrome or reversible encephalopathy due to sudden forced dilatation of cerebral arteries in response to overproduction of vasodilators disrupting the blood brain barrier and cause extravasation of fluid and resulting edema and unilateral effecement of hemispheric cortical sulci. However still it remain unexplained that why the blood brain barrier affected only on one side.