Friday 5 August 2011

Hippocampal sclerosis MRI

21 yo male under treatment for epilepsy, seizure once every 2-3 months which seems to be left adversive with secondary generalization. He is on Phenytoin 300mg 1---0

Oblique coronal T2w and T1w SPGR for medial temporal lobes.

Subjective evaluation of size and signal of hippocampi show left hippocampus with smaller volume implies to atrophy with faint T2 hyperintensity compared to right side.
Hippocampal sclerosis needs consideration with clinical and EEG correlation.

Mesial temporal sclerosis 

Syn : MTS, hippocampal sclerosis (HS), Ammon horn sclerosis.

A seizure associated neuronal loss and gliosis in hippocampus.

CT is typically normal as is insensitive to MTS. MRI is investigation of choice.
Hippocampal atrophy with abnormal T2 hyperintenssity is a diagnostic clue.
Atrophy of fornix mamillary body, enlarged ipsilateral temporal horn of lateral ventricle, loss of hippocampal head digitations, atrophy of white matter in parahippocampal gyrus, increased T2 signal in anterior temporal white matter may be the additional associated findings.

In Mesial temporal lobe, Hippocampus is most commonly involved followed by amygdala > fornix > mamillary bodies. Involvement is bilateral in 20% of cases.

Etiology is controversial, may be acquired or developmental. Likely that MTS represents a common outcome of both acquired and developmental processes. Acquired causes related to changes after prolonged febrile seizures, status epilepticus, complicated delivery and ischemia.Familial cases of mesial temporal lobe epilepsy have been reported.

Microscopic features are decrease in hippocampal neurons and gliosis.
Chronic astrogliosis with a fine fibrillary background containing bland nuclei of astrocytes and few remaining neurons.
CA1, CA4, and CA3 are most affected. May involve entire cornu ammonis and dentate gyrus.

Dual pathology occurs in 15% of cases of MTS . Cortical dysplasia is most common dual pathology.

Clinical presentation: Complex partial seizure is the most common signs/symptoms, may progress to tonic-clonic seizures. Disease of childhood, young adults with no gender predominance.

EEG often helpful for lesion localization in 60-90%.

Medical treatment successful in only 25%.
Anterior temporal lobe resection for medically intractable disease.
Anterior temporal lobectomy successful in 70-95% patients with MR findings of MTS
If MR is normal, success of anterior temporal lobectomy is 40-55%
If amygdala involved, decreased success of surgery,approximately 50%
Resection includes anterior temporal lobe, majority of hippocampus, variable portions of amygdala.

Reference : Diagnostic imaging Osborn.

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