Asymmetric Cerebral Hemispheres



Asymmetric Cerebral Hemispheres


Gregory L. Katzman, MD, MBA



DIFFERENTIAL DIAGNOSIS


Common



  • Normal Variant


  • Encephalomalacia, General



    • Post-Ischemic Encephalomalacia


    • Post-Traumatic Encephalomalacia


    • Post-Inflammatory Encephalomalacia


  • Contusion/Traumatic Cerebral Edema


  • Cerebral Ischemia-Infarction, Acute


  • Cerebral Infarction, Chronic


  • Alzheimer Dementia


  • Multi-Infarct Dementia


  • CMV, Congenital


  • Frontotemporal Dementia


  • Dyke-Davidoff-Masson


Less Common



  • Hypoxic Ischemic Encephalopathy


  • Encephalitis


  • Sturge-Weber Syndrome


  • Plagiocephaly


  • MELAS


  • Hemimegalencephaly of Tuberous Sclerosis


Rare but Important



  • Hemimegalencephaly (Sporadic or Familial)


  • Pachygyria-Polymicrogyria


  • Gliomatosis Cerebri


  • Epidermal Nevus Syndrome


  • Schizencephaly


  • Encephalocraniocutaneous Lipomatosis


  • Proteus Syndrome


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Differential diagnosis list is vast and could logically be subdivided as follows



    • One hemisphere larger than the other


    • One hemisphere smaller than the other


Helpful Clues for Common Diagnoses



  • Normal Variant



    • Minor asymmetry of otherwise normal appearing density/intensity parenchyma


    • Substantial individual diversity of left-right gyral cerebral cortex asymmetries


    • Cerebral asymmetry patterns are not universal & show variation based on origin


  • Encephalomalacia, General



    • All etiologies appear as CSF replacing destroyed parenchyma due to



      • Post-ischemic loss of tissue following parenchymal hypoxic cell death


      • Post-traumatic loss from parenchymal irreversible traumatic insult


      • Post-inflammatory loss by irreversibly injured tissue


    • Post-Traumatic Encephalomalacia



      • Parenchymal loss replaced by CSF


      • Occur in characteristic locations where brain is adjacent to bony protuberance or dural fold


  • Contusion/Traumatic Cerebral Edema



    • Patchy superficial hemorrhages within edematous background, loss of gray-white distinction


    • Swelling with loss of sulci, fissures, & cisterns


  • Cerebral Ischemia-Infarction, Acute



    • Early cortical swelling in defined vascular distribution(s)


    • DWI restriction with correlating ADC map


  • Cerebral Infarction, Chronic



    • Volume loss with gliosis along margins


    • Loss in a defined vascular distribution


  • Alzheimer Dementia



    • Parietal & temporal cortical atrophy with disproportionate hippocampal volume loss


    • Often affects brain asymmetrically


  • Multi-Infarct Dementia



    • Multifocal infarcts of gray matter, white matter, basal ganglia, pons


    • Usually bilateral, but may be unilateral


  • CMV, Congenital



    • Microcephaly, cerebral calcification, cortical gyral abnormalities, cerebellar hypoplasia, & myelin delay or destruction


    • Gestational age at time of infection determines pattern of CNS injury


  • Frontotemporal Dementia



    • Caused by focal cortical atrophy involving frontal &/or temporal lobes


    • Worse atrophy of dominant hemisphere


  • Dyke-Davidoff-Masson



    • Cerebral hemiatrophy with ipsilateral hypertrophy of the skull and sinuses


    • Caused by an intrauterine or perinatal carotid artery infarction


Helpful Clues for Less Common Diagnoses



  • Hypoxic Ischemic Encephalopathy



    • Acquired neonatal condition generally attributed to cerebral hypoperfusion



    • Several brain injury patterns attributed to differing clinical variables


  • Encephalitis



    • Abnormal T2 hyperintensity of gray matter ± white matter, or deep gray nuclei


    • Diffuse brain parenchymal inflammation caused by a variety of pathogens, most commonly viruses


  • Sturge-Weber Syndrome



    • Cortical Ca++, atrophy, and enlarged ipsilateral choroid plexus


    • Unilateral 80%, bilateral 20%; occipital > parietal > frontal/temporal lobes > diencephalon/midbrain > cerebellum


  • Plagiocephaly



    • CT: Osseous asymmetry with thickened & sclerotic suture margins


    • Premature unilateral closure of coronal &/or lambdoidal sutures


  • MELAS



    • Stroke-like cortical lesions crossing typical vascular territories


    • Acute → gyriform swelling; chronic → atrophy


  • Hemimegalencephaly of Tuberous Sclerosis



    • Unilateral lobar/hemispheric overgrowth


    • Look for other markers of TSC (e.g., subependymal nodules)


Helpful Clues for Rare Diagnoses



  • Hemimegalencephaly (Sporadic or Familial)



    • Hamartomatous overgrowth of hemisphere


    • Defect of cellular organization, neuronal migration


  • Pachygyria-Polymicrogyria



    • Findings range from incomplete lissencephaly to excessively small & prominent gyral convolutions


    • Disorder of neuronal migration


  • Gliomatosis Cerebri



    • T2 hyperintense infiltrating mass with enlargement of involved hemisphere


    • Typically hemispheric white matter involvement, involves cortex in 19%


  • Epidermal Nevus Syndrome



    • Hemimegalencephaly is most common CNS abnormality


    • Also migration abnormalities, vascular malformations, corpus callosal agenesis, Dandy-Walker, myelomeningocele, Chiari malformations, & tumors


  • Schizencephaly



    • Transmantle gray matter lined clefts


    • “Closed-lip” (small) or “open-lip” (large)


  • Encephalocraniocutaneous Lipomatosis



    • Hemispheric atrophy, ventriculomegaly with ipsilateral alopecia overlying a scalp lipoma


    • Hydrocephalus is frequently present


  • Proteus Syndrome



    • Complex hamartomatous disorder involving half the body


    • CNS: Hemimegalencephaly, subependymal calcified nodules, & periventricular cysts






Image Gallery









Axial T2WI MR shows normal asymmetry, especially involving the left temporal/occipital lobes image as compared to the right, in this patient with headache and a normal MR.






Axial T2WI MR shows typical MCA distribution chronic infarct as encephalomalacia with gliotic hyperintense margins image. Adjacent sulci & ventricle image are prominent from volume loss.







(Left) Axial NECT demonstrates post-traumatic encephalomalacia of bilateral rectus gyri image & left temporal tip image in characteristic locations adjacent to bony surfaces. (Right) Axial T1 C+ MR shows extensive cavitation of bilateral hemispheric white matter image with extreme volume loss and cavity retraction bilaterally, right more than left, all sequelae from Citrobacter meningitis.

Only gold members can continue reading. Log In or Register to continue

Aug 7, 2016 | Posted by in NEUROLOGY | Comments Off on Asymmetric Cerebral Hemispheres
Premium Wordpress Themes by UFO Themes