University of Missouri Radiology Department
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December, 2010




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Web Publication No 10.
 
Pragati Kumar MD, Amolak Singh, MD
 
Clinical Presentation:

39 year old male with intractable seizures. Right hemispheric epilepsy.

 
Presurgical Workup:
FDG PET- CT  and MRI of the brain were performed.
 

Images 1, 2 and 3: FDG –PET shows increased FDG uptake in the right frontal  lobe subcortical zone. Mildy decreased uptake in the overlying frontal cortex.

 

Images 4, 5 and 6: Axial T2 weighted images of the brain show multifocal right frontal and temporal lobe gray matter heterotopia. The right cerebral hemisphere is smaller than the left.

 
Definition:

-Arrested/disrupted neurons along migration path from periventricular germinal   zone to cortex
-Can be inherited
-Can be acquired (maternal trauma, infection, or toxin

 
Imaging Findings :

Nodule or ribbon on MR, isointense with gray matter (GM), "stuck" in wrong place (+/- thin overlying cortex)

Subependymal heterotopia (most common)
Band heterotopia ("double cortex")
Lissencephaly type 1
Lissencephaly type 2 ("cobblestone")
Subcortical heterotopia: Large foci have thinned and dysplastic overlying cortex, small foci don't

FDG uptake in region of HGM usually similar to normal cortex (also slightly greater or slightly less)
FDG uptake in overlying normal cortex may be decreased
Identification of seizure focus within HGM: Interictal FDG PET (isocortical metabolism) plus ictal SPECT ("hot") superior to all other modalities

SPECT
Tc-99m hexamethylpropyleneamine oxime (HMPAO), bicisate
Interictal: Uptake similar to normal cortex
Ictal: Focal increased uptake with spread to overlying cortex

 

  • increased uptake with spread to overlying cortex
  • Top Differential Diagnoses
  • Normal Gray Matter
  • Tumors
  • Tuberous Sclerosis
  • Zellweger Syndrome (Peroxisomal Disorder)
  • Cytomegalovirus

Presentation

  • Most common signs/symptoms: Cognitive function, age of seizure (Sz) onset/severity depend on location/amount of abnormally positioned GM
  • Clinical profile: Young child with developmental delay and Sz

 

Demographics

  • Age
    • Severe cases present in infancy with Sz & associated malformations
    • Mild cases or simple subcortical nodules can be asymptomatic and only incidental findings on imaging or autopsy
  • Gender: Males with X-linked disorders have significantly worse brain malformation and outcome

Natural History & Prognosis

  • Variable life span dependent upon extent of malformation
    • Type 2 lissencephaly: Months
    • Focal heterotopias: Can be normal (depends on Sz control)
    •  

Treatment

  • Surgery reserved for intractable Sz
    • Resect small accessible epileptogenic nodules
    • Corpus callosotomy if bilateral or diffuse unresectable lesions

 

 
 
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