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Mesial Temporal Sclerosis
KEY FACTS
Terminology
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Seizure-associated neuronal loss and gliosis in hippocampus and adjacent structures
Imaging
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Primary features: Abnormal T2 hyperintensity, hippocampal volume loss/atrophy, obscuration of internal architecture
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Secondary signs: Ipsilateral fornix and mammillary body atrophy, enlarged ipsilateral temporal horn, and choroidal fissure
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↑ hyperintensity on DWI (T2 shine through)
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↓ NAA in hippocampus, temporal lobe
Top Differential Diagnoses
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Status epilepticus
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Low-grade astrocytoma
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Choroidal fissure cyst
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Hippocampal sulcus remnant
Pathology
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Prolonged febrile seizures may produce acute hippocampal injury → subsequent atrophy
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Coexistent 2nd developmental lesion in 15% of mesial temporal sclerosis (MTS) patients
Clinical Issues
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Partial complex seizures
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Often history of childhood febrile or medically intractable seizures
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Surgical temporal lobectomy reserved for medically intractable seizures, intolerable drug side effects
Diagnostic Checklist
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Most common cause of partial complex epilepsy in adult age group
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Low-grade neoplasms and cortical dysplasia more common causes of partial complex epilepsy than MTS in pediatric age group
Coronal graphic depicts the characteristic appearance of mesial temporal sclerosis. The right hippocampus
is small (atrophic) with loss of normal internal architecture reflecting neuronal loss and gliosis. Note concordant atrophy of the ipsilateral fornix
and widening of the ipsilateral temporal horn and choroidal fissure
.
is small (atrophic) with loss of normal internal architecture reflecting neuronal loss and gliosis. Note concordant atrophy of the ipsilateral fornix and widening of the ipsilateral temporal horn and choroidal fissure .
Coronal STIR MR at 3.0 tesla in a normal nonepileptic patient imaged for headaches demonstrates normal bilateral hippocampal anatomy
, size, and signal intensity.
, size, and signal intensity.
Coronal T1-weighted true inversion recovery MR at 3.0 tesla shows asymmetric right hippocampal volume loss
and obscuration of normal internal gray-white differentiation. The ipsilateral fornix
is smaller than the normal left fornix.
and obscuration of normal internal gray-white differentiation. The ipsilateral fornix is smaller than the normal left fornix.
Coronal T2-weighted MR at 3.0 tesla in the same patient with right hippocampal sclerosis
shows hippocampal volume loss and obscuration of normal internal architecture but normal T2 signal intensity. FLAIR better shows the increase in signal intensity.
shows hippocampal volume loss and obscuration of normal internal architecture but normal T2 signal intensity. FLAIR better shows the increase in signal intensity.
TERMINOLOGY
Abbreviations
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Mesial temporal sclerosis (MTS)
Synonyms
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Ammons horn sclerosis, hippocampal sclerosis (HS)
Definitions
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Seizure-associated neuronal loss and gliosis in hippocampus and adjacent structures
IMAGING
General Features
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Best diagnostic clue
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Primary features: Abnormal T2 hyperintensity, hippocampal volume loss/atrophy, obscuration of internal architecture
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Secondary signs: Ipsilateral fornix and mammillary body atrophy, enlarged ipsilateral temporal horn, and choroidal fissure
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Additional findings: Loss of ipsilateral hippocampal head (pes) digitations, parahippocampal gyrus white matter atrophy, ↑ T2 signal in anterior temporal white matter
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Location
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Mesial temporal lobe(s), 10-20% bilateral
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Hippocampus > amygdala > fornix > mammillary bodies
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Size
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Slight to marked ↓ in hippocampal volume
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Morphology
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Abnormal shape, size of affected hippocampus
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