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title: "Mesial Temporal Sclerosis"
docid: "3861ee73-c82c-49f2-a60f-8fd08f7e6165"
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value: "Kevin R. Moore, MD"
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pageDescription: "Mesial Temporal Sclerosis"
pageKeywords: "Brain, Diagnosis, Pathology-Based Diagnoses, Acquired Toxic/Metabolic/Degenerative Disorders, Toxic, Metabolic, Nutritional, Systemic Diseases With CNS Manifestations, Mesial Temporal Sclerosis"
pageTitle: "Mesial Temporal Sclerosis | STATdx"
enhancedTitle: "Mesial Temporal Sclerosis"
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- "Mesial Temporal Sclerosis"
---
# KEY FACTS
- ## Terminology
- Seizure-associated neuronal loss & gliosis in hippocampus & adjacent structures
- ## Imaging
- Primary features: Abnormal T2 hyperintensity, hippocampal volume loss/atrophy, obscuration of internal architecture
- Secondary signs: Ipsilateral fornix & mammillary body atrophy, enlarged ipsilateral temporal horn, & choroidal fissure
- ↑ hyperintensity on DWI (T2 shine-through)
- ↓ NAA in hippocampus, temporal lobe
- ## Top Differential Diagnoses
- Status epilepticus
- Low-grade astrocytoma
- Choroidal fissure cyst
- Hippocampal sulcus remnant
- Focal cortical dysplasia
- ## Pathology
- Prolonged febrile seizures may produce acute hippocampal injury → subsequent atrophy
- Coexistent 2nd developmental lesion in 15% of patients with mesial temporal sclerosis (MTS)
- ## Clinical Issues
- Partial complex seizures
- Often history of childhood febrile or medically intractable seizures
- Surgical temporal lobectomy reserved for medically intractable seizures, intolerable drug side effects
- ## Diagnostic Checklist
- Most common cause of partial complex epilepsy in adult age group
- Low-grade neoplasms & focal cortical dysplasia more common causes of partial complex epilepsy than MTS in pediatric age group
# TERMINOLOGY
- ## Abbreviations
- Mesial temporal sclerosis (MTS)
- ## Synonyms
- Ammon horn sclerosis, hippocampal sclerosis (HS)
- ## Definitions
- Seizure-associated neuronal loss & gliosis in hippocampus & adjacent structures
# IMAGING
- ## General Features
- ### Best diagnostic clue
- Primary features: Abnormal T2 hyperintensity, hippocampal volume loss/atrophy, obscuration of internal architecture
- Secondary signs: Ipsilateral fornix & mammillary body atrophy, enlarged ipsilateral temporal horn, & choroidal fissure
- Additional findings: Loss of ipsilateral hippocampal head (pes) digitations, parahippocampal gyrus white matter (WM) atrophy, ↑ T2 signal in anterior temporal WM
- ### Location
- Mesial temporal lobe(s), 15-20% bilateral but usually asymmetric
- Hippocampus > amygdala > fornix > mammillary bodies
- ### Size
- Slight to marked ↓ in hippocampal volume
- ### Morphology
- Abnormal shape, size of affected hippocampus
- ## CT Findings
- ### NECT
- Usually normal; CT insensitive to MTS
- ## MR Findings
- ### T1WI
- ↓ hippocampal size
- Loss of normal hippocampal gray-white differentiation
- ± ipsilateral fornix, mammillary body atrophy
- Quantitative hippocampal volumetry: ↑ sensitivity of MTS detection (particularly bilateral MTS)
- ### T2WI
- Hippocampal atrophy
- Obscuration of normal internal architecture
- ↑ hippocampal signal intensity
- ± ipsilateral fornix, mammillary body atrophy, dilatation of ipsilateral temporal horn
- ± abnormal hyperintensity, volume loss in ipsilateral anterior temporal lobe
- ### FLAIR
- Hyperintense signal in abnormal hippocampus
- ### DWI
- ↑ hyperintensity on DWI (T2 shine-through)
- ↑ diffusivity on ADC
- DTI: ↓ fractional anisotropy affecting widespread WM tracts, extensive areas with ↑ radial diffusivities independent of disease side
- ### T1WI C+
- No enhancement
- ### MRS
- ↓ NAA in hippocampus, temporal lobe
- ↓ NAA/Cho & ↓ NAA/Cho+Cr suggests MTS
- ± lactate/lipid peaks after 24 hours of continual seizure
- ## Angiographic Findings
- Presurgical Wada testing: Neuropsychologic testing after intracarotid amobarbital (Amytal) injection
- Lateralize memory & language functions
- Predict postoperative memory loss, feasibility of surgery
- May help lateralize seizure onset
- fMRI mapping replacing Wada testing
- ## Nuclear Medicine Findings
- FDG PET: Hypometabolism in abnormal mesial temporal lobe
- SPECT: Hypoperfusion (interictal) or hyperperfusion (ictal) in epileptogenic zone (EZ)
- Sensitivity of ictal > interictal
- ## Imaging Recommendations
- ### Best imaging tool
- High-resolution MR imaging
- MRS, quantitative volumetry may help lateralize MTS in difficult cases
- ### Protocol advice
- Thin-section coronal T2WI & FLAIR (3 mm), coronal 3D SPGR (1-2 mm), angled perpendicular to long axis of hippocampus
# DIFFERENTIAL DIAGNOSIS
- [Status Epilepticus](/document/status-epilepticus/a058b733-4b80-46a1-8097-d68685ecf921)
- Clinical history of multiple seizures or status epilepticus
- Temporary T2 hyperintensity ± gyriform enhancement in affected cortex, hippocampus
- ## Low-Grade Astrocytoma
- Hyperintense temporal lobe WM mass (usually nonenhancing)
- ± seizures, young adults typical
- [Choroidal Fissure Cyst](/document/choroid-fissure-cyst/f60887bb-f021-401f-80b2-1d79e0a758e5)
- Asymptomatic CSF signal cyst in choroidal fissure distorts normal hippocampus
- Round on axial, coronal images
- Oval, parallels temporal lobe long axis on sagittal imaging
- No abnormal T2 hyperintensity in mesial temporal lobe
- [Hippocampal Sulcus Remnant](/document/hippocampal-sulcus-remnant-cysts/3b54dc78-2c77-4cbb-9ab4-e5c6f5d8b228)
- Failure of normal hippocampal sulcus involution → asymptomatic cyst between dentate gyrus, cornu ammonis (CA)
- Common normal variant (10-15%)
- [Cavernous Malformation](/document/cavernous-malformation/d6c0dfc6-25d3-4713-941f-373c68ca8f0d)
- Heterogeneous hyperintense "popcorn" lesion with dark complete hemosiderin rim
- ± seizures
- ## Dysembryoplastic Neuroepithelial Tumor
- [Demarcated "bubbly," variably enhancing cortical mass ± regional cortical dysplasia](/document/dnet/30baaad9-4835-4cf0-8b95-974d6517511e)
- Partial complex seizures
- [Focal Cortical Dysplasia](/document/focal-cortical-dysplasia/046564e0-5bb7-4f23-8a3e-010a68cfbafe)
- Most common dual pathology associated with MTS
- T2 hyperintensity in anterior temporal WM
# PATHOLOGY
- ## General Features
- ### Etiology
- Controversial whether acquired or developmental
- Acquired: Follows complicated febrile seizures (FS), status epilepticus, encephalitis
- Developmental: 2nd developmental lesion identified in 15%
- 2-hit hypothesis: (1) Initial precipitating injury (like complicated seizures), (2) ↑ vulnerability (such as genetic predisposition or developmental anomaly)
- Most likely MTS represents common outcome of both acquired & developmental processes
- FS most common childhood seizure disorder (2-5%)
- Prolonged FS may produce acute hippocampal injury → subsequent atrophy
- ### Genetics
- Familial cases of mesial temporal lobe epilepsy (TLE), FS reported
- Recent studies suggest relationship between FS & later epilepsy development may be genetic
- Syndrome-specific genes for FS (channelopathies) account for small proportion of FS cases
- ### Associated abnormalities
- Coexistent 2nd developmental lesion (15%)
- ## Gross Pathologic & Surgical Features
- Normal hippocampus divided anatomically into head (pes), body, tail
- Subdivision into Ammon horn, dentate gyrus, hippocampal sulcus, fimbria, alveus, subiculum, parahippocampal gyrus, collateral sulcus
- Mesial temporal lobe atrophy: Hippocampal body (85-90%), tail (60%), head (50%), amygdala (10%)
- Absence of hemorrhage or necrosis
- HS described by gross pathologists as shrunken & hardened hippocampus with characteristic histologic neuronal loss, glial proliferation
- ## Microscopic Features
- Chronic astrogliosis with fine fibrillary background of bland astrocytic nuclei & ↓ residual neurons
- Selective loss of inhibitory interneurons, abnormal axonal sprouting, reorganization of neural transmitter receptors, alterations in 2nd messenger systems, & hyperexcitability of granule cells
- Ammon horn, CA, contains 4 zones of granular cells: CA1, CA2, CA3, CA4
- CA1, CA4 pyramidal cell layers most susceptible to ischemia
- All hippocampal regions may show varying neuronal cell loss
# CLINICAL ISSUES
- ## Presentation
- ### Most common signs/symptoms
- Partial complex seizures, automatisms
- Simple at younger ages, increasingly complex & discrete with age
- Motor manifestations ↓ with ↑ age; less abundant in adults
- ### Other signs/symptoms
- May progress to generalized tonic-clonic seizures
- ### Clinical profile
- Often history of childhood febrile or medically intractable seizures
- History of complex or prolonged FS ↑ risk for development of hippocampal injury, MTS
- Surface electro- (EEG) or magneto- (MEG) encephalogram helpful for localization (60-90%)
- Intracranial EEG (subdural or depth electrodes) may be indicated if noninvasive studies discordant
- ## Demographics
- ### Age
- Disease of older children, young adults
- ### Sex
- No sex predominance
- ### Epidemiology
- MTS accounts for majority of epilepsy patients undergoing temporal lobe seizure surgery
- ## Natural History & Prognosis
- Anterior temporal lobectomy 70-90% successful in MTS, 40-55% if MR normal
- ↓ surgical success when amygdala involved
- ## Treatment
- Clinical management based on phenotypic features of initial febrile & subsequent seizures
- Medical treatment initial approach
- Surgical temporal lobectomy reserved for medically intractable seizures, intolerable drug side effects
- Resection includes anterior temporal lobe, majority of hippocampus, variable portions of amygdala
- Surgical resection of EZ
- MR-guided laser interstitial thermal therapy (MRgLITT) less invasive option for stereotactic ablation of EZ
# DIAGNOSTIC CHECKLIST
- ## Consider
- Most common cause of partial complex epilepsy in adults
- Bilateral in 15-20%; difficult to detect without quantitative volumetry unless severe
- MTS imaging findings not found in normal seizure-free patients (controversial)
- ## Image Interpretation Pearls
- Coronal high-resolution T2WI, FLAIR MR most sensitive for MTS; dual pathology in 15%
- In pediatric age group, low-grade neoplasms & cortical dysplasia more common causes of partial complex epilepsy than MTS
f1594712-2ab3-4d9e-9a3d-a75b51f1c879
## References
# Selected References
1. [Hsu CCT et al: Imaging the patient with epilepsy. In Hodler J et al: Diseases of the Brain, Head & Neck, Spine 2020-23. Diagnostic Imaging. Springer, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32119252%5Bpmid%5D)
1. [Strnad BS et al: An image processing algorithm to aid diagnosis of mesial temporal sclerosis in children: a case-control study. Pediatr Radiol. 50(1):98-106, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=31578627%5Bpmid%5D)
1. [Youngerman BE et al: Magnetic resonance imaging-guided laser interstitial thermal therapy for epilepsy: systematic review of technique, indications, and outcomes. Neurosurgery. 86(4):E366-82, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=31980831%5Bpmid%5D)
1. [Dahi F et al: Image processing to improve detection of mesial temporal sclerosis in adults. AJNR Am J Neuroradiol. 40(5):798-801, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=30948379%5Bpmid%5D)
1. [Mettenburg JM et al: Improved detection of subtle mesial temporal sclerosis: validation of a commercially available software for automated segmentation of hippocampal volume. AJNR Am J Neuroradiol. 40(3):440-5, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=30733255%5Bpmid%5D)
1. [Chong S et al: Surgical treatment of lesional mesial temporal lobe epilepsy. J Epilepsy Res. 8(1):6-11, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=30090756%5Bpmid%5D)
1. [Corrêa DG et al: Widespread white matter DTI alterations in mesial temporal sclerosis independent of disease side. Epilepsy Behav. 87:7-13, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=30149360%5Bpmid%5D)
1. [Azab M et al: Mesial temporal sclerosis: accuracy of NeuroQuant versus Neuroradiologist. AJNR Am J Neuroradiol. 36(8):1400-6, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=25907519%5Bpmid%5D)
1. [Hamelin S et al: Revisiting hippocampal sclerosis in mesial temporal lobe epilepsy according to the "two-hit" hypothesis. Rev Neurol (Paris). 171(3):227-35, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=25748332%5Bpmid%5D)
1. [French JA et al: Can febrile status cause hippocampal sclerosis? Ann Neurol. 75(2):173-4, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24443389%5Bpmid%5D)
1. [Roessler K et al: Improved resection in lesional temporal lobe epilepsy surgery using neuronavigation and intraoperative MR imaging: favourable long term surgical and seizure outcome in 88 consecutive cases. Seizure. 23(3):201-7, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24355699%5Bpmid%5D)
1. [Thom M: Review: Hippocampal sclerosis in epilepsy: a neuropathology review. Neuropathol Appl Neurobiol. 40(5):520-43, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24762203%5Bpmid%5D)
1. [Kapina V et al: Hippocampal sclerosis and chronic epilepsy following posterior reversible encephalopathy syndrome. Epileptic Disord. 15(4):451-4, 2013](http://www.ncbi.nlm.nih.gov/pubmed/?term=24515311%5Bpmid%5D)
1. [Blümcke I et al: Defining clinico-neuropathological subtypes of mesial temporal lobe epilepsy with hippocampal sclerosis. Brain Pathol. 22(3):402-11, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=22497612%5Bpmid%5D)
1. [Bonilha L et al: Subtypes of medial temporal lobe epilepsy: influence on temporal lobectomy outcomes? Epilepsia. 53(1):1-6, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=22050314%5Bpmid%5D)
1. [Malmgren K et al: Hippocampal sclerosis--origins and imaging. Epilepsia. 53 Suppl 4:19-33, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=22946718%5Bpmid%5D)
1. [Kröll-Seger J et al: Non-paraneoplastic limbic encephalitis associated with antibodies to potassium channels leading to bilateral hippocampal sclerosis in a pre-pubertal girl. Epileptic Disord. 11(1):54-9, 2009](http://www.ncbi.nlm.nih.gov/pubmed/?term=19251579%5Bpmid%5D)
1. [Bote RP et al: Hippocampal sclerosis: histopathology substrate and magnetic resonance imaging. Semin Ultrasound CT MR. 29(1):2-14, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=18383904%5Bpmid%5D)
1. [Chang YC et al: Long-term neuroplasticity effects of febrile seizures in the developing brain. Chang Gung Med J. 31(2):125-35, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=18567412%5Bpmid%5D)
1. [Focke NK et al: Voxel-based diffusion tensor imaging in patients with mesial temporal lobe epilepsy and hippocampal sclerosis. Neuroimage. 40(2):728-37, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=18261930%5Bpmid%5D)
1. [Carne RP et al: 'MRI-negative PET-positive' temporal lobe epilepsy (TLE) and mesial TLE differ with quantitative MRI and PET: a case control study. BMC Neurol. 7:16, 2007](http://www.ncbi.nlm.nih.gov/pubmed/?term=17588263%5Bpmid%5D)
1. [Ray A et al: Temporal lobe epilepsy in children: overview of clinical semiology. Epileptic Disord. 7(4):299-307, 2005](http://www.ncbi.nlm.nih.gov/pubmed/?term=16338672%5Bpmid%5D)
1. [Ray A et al: Treatment options and paradigms in childhood temporal lobe epilepsy. Expert Rev Neurother. 5(6):785-801, 2005](http://www.ncbi.nlm.nih.gov/pubmed/?term=16274336%5Bpmid%5D)
1. [Sloviter RS: The neurobiology of temporal lobe epilepsy: too much information, not enough knowledge. C R Biol. 328(2):143-53, 2005](http://www.ncbi.nlm.nih.gov/pubmed/?term=15771000%5Bpmid%5D)
1. [Cendes F: Febrile seizures and mesial temporal sclerosis. Curr Opin Neurol. 17(2):161-4, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=15021243%5Bpmid%5D)
1. [Theodore WH: Recent advances and trends in epilepsy imaging: pathogenesis and pathophysiology. Rev Neurol Dis. 1(2):53-9, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=16400258%5Bpmid%5D)
1. [Van Paesschen W: Qualitative and quantitative imaging of the hippocampus in mesial temporal lobe epilepsy with hippocampal sclerosis. Neuroimaging Clin N Am. 14(3):373-400, vii, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=15324854%5Bpmid%5D)
1. [Volcy Gómez M: [Mesial temporal lobe epilepsy: its physiopathology, clinical characteristics, treatment and prognosis] Rev Neurol. 38(7):663-7, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=15098189%5Bpmid%5D)
1. [Bocti C et al: The pathological basis of temporal lobe epilepsy in childhood. Neurology. 60(2):191-5, 2003](http://www.ncbi.nlm.nih.gov/pubmed/?term=12552029%5Bpmid%5D)
1. [Sokol DK et al: From swelling to sclerosis: acute change in mesial hippocampus after prolonged febrile seizure. Seizure. 12(4):237-40, 2003](http://www.ncbi.nlm.nih.gov/pubmed/?term=12763472%5Bpmid%5D)
1. [Benbadis SR et al: MRI evidence of mesial temporal sclerosis in subjects without seizures. Seizure. 11(5):340-3, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12076108%5Bpmid%5D)
1. [Capizzano AA et al: Multisection proton MR spectroscopy for mesial temporal lobe epilepsy. AJNR Am J Neuroradiol. 23(8):1359-68, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12223379%5Bpmid%5D)
1. [Kumlien E et al: Treatment outcome in patients with mesial temporal sclerosis. Seizure. 11(7):413-7, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12237065%5Bpmid%5D)
1. [Kuzniecky RI et al: Neuroimaging of epilepsy. Semin Neurol. 22(3):279-88, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12528053%5Bpmid%5D)
1. [Lewis DV et al: Do prolonged febrile seizures produce medial temporal sclerosis? Hypotheses, MRI evidence and unanswered questions. Prog Brain Res. 135:263-78, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12143347%5Bpmid%5D)
1. [Scott RC et al: Magnetic resonance imaging findings within 5 days of status epilepticus in childhood. Brain. 125(Pt 9):1951-9, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12183341%5Bpmid%5D)
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1. [Bronen RA et al: Regional distribution of MR findings in hippocampal sclerosis. AJNR Am J Neuroradiol. 16(6):1193-200, 1995](http://www.ncbi.nlm.nih.gov/pubmed/?term=7677010%5Bpmid%5D)
## Images
### Selected Images
![Coronal graphic depicts the characteristic appearance of mesial temporal sclerosis (MTS). The right hippocampus <img src='img/arrows/CO.png'/> is small (atrophic) with loss of normal internal architecture, reflecting neuronal loss and gliosis. Note concordant atrophy of the ipsilateral fornix <img src='img/arrows/CS.png'/> and widening of the ipsilateral temporal horn and choroidal fissure.](images/app.statdx.com_image_thumbnail_7d1af415-dfe9-43d5-b1fc-066a3bf8596b_annotated_true_size_900_quality_90_036a6961a4b8720aa4a9dff2b22d51cabee4f91e.jpg)
*Coronal graphic depicts the characteristic appearance of mesial temporal sclerosis (MTS). The right hippocampus <img src='img/arrows/CO.png'/> is small (atrophic) with loss of normal internal architecture, reflecting neuronal loss and gliosis. Note concordant atrophy of the ipsilateral fornix <img src='img/arrows/CS.png'/> and widening of the ipsilateral temporal horn and choroidal fissure.*
![Coronal T2 MR at 3.0T demonstrates normal bilateral hippocampal anatomy <img src='img/arrows/CC.png'/>, size, and signal intensity. Note distinct layers of gray and white matter in the hippocampus.](images/app.statdx.com_image_thumbnail_5a791ed0-a397-49d3-9136-42f932e8575f_annotated_true_size_900_quality_90_94cab71fb76799e82e9e64fe2c4dfa6abb3d50ff.jpg)
*Coronal T2 MR at 3.0T demonstrates normal bilateral hippocampal anatomy <img src='img/arrows/CC.png'/>, size, and signal intensity. Note distinct layers of gray and white matter in the hippocampus.*
![Coronal T1 true inversion recovery MR at 3.0T shows asymmetric right hippocampal volume loss <img src='img/arrows/CS.png'/> and obscuration of normal internal gray-white differentiation. The ipsilateral fornix <img src='img/arrows/CC.png'/> is smaller than the normal left fornix.](images/app.statdx.com_image_thumbnail_71823a62-6d76-4742-b5ff-1d85bf0f8431_annotated_true_size_900_quality_90_a9eea9db237ba0a5f39aeced5764882a73552503.jpg)
*Coronal T1 true inversion recovery MR at 3.0T shows asymmetric right hippocampal volume loss <img src='img/arrows/CS.png'/> and obscuration of normal internal gray-white differentiation. The ipsilateral fornix <img src='img/arrows/CC.png'/> is smaller than the normal left fornix.*
![Coronal T2 MR at 3.0T in the same patient with right hippocampal sclerosis (HS) <img src='img/arrows/CS.png'/> shows hippocampal volume loss and obscuration of normal internal architecture but normal T2 signal intensity. FLAIR better shows the increase in signal intensity.](images/app.statdx.com_image_thumbnail_07c5b79f-0792-4872-b20a-8d5090303401_annotated_true_size_900_quality_90_9e3035fdd5e6039063552a0e48822ba21a2a0f6e.jpg)
*Coronal T2 MR at 3.0T in the same patient with right hippocampal sclerosis (HS) <img src='img/arrows/CS.png'/> shows hippocampal volume loss and obscuration of normal internal architecture but normal T2 signal intensity. FLAIR better shows the increase in signal intensity.*
![Coronal T2 MR in a patient with epilepsy shows a vertical left collateral sulcus <img src='img/arrows/CS.png'/> and a globular hippocampus <img src='img/arrows/CC.png'/>. This common variation is due to failure of hippocampal inversion.](images/app.statdx.com_image_thumbnail_94bc080d-63d6-48ab-9abb-da369015f505_annotated_true_size_900_quality_90_d9f3bda3d2fbd5b11890a9c80badccd7341abeba.jpg)
*Coronal T2 MR in a patient with epilepsy shows a vertical left collateral sulcus <img src='img/arrows/CS.png'/> and a globular hippocampus <img src='img/arrows/CC.png'/>. This common variation is due to failure of hippocampal inversion.*
![Coronal T2 MR in a patient with temporal lobe epilepsy demonstrates primary and secondary imaging features of MTS. There is severe left hippocampal atrophy and hyperintensity <img src='img/arrows/CC.png'/>. Secondary features are atrophy of the left fornix <img src='img/arrows/CS.png'/> and mammillary body <img src='img/arrows/WS.png'/> as well as dilation of temporal horn <img src='img/arrows/CO.png'/>.](images/app.statdx.com_image_thumbnail_02ff763e-4461-4fa8-8e1e-777ae26bb1a6_annotated_true_size_900_quality_90_69c45cf047e85d16f79d487a42d986972570f60d.jpg)
*Coronal T2 MR in a patient with temporal lobe epilepsy demonstrates primary and secondary imaging features of MTS. There is severe left hippocampal atrophy and hyperintensity <img src='img/arrows/CC.png'/>. Secondary features are atrophy of the left fornix <img src='img/arrows/CS.png'/> and mammillary body <img src='img/arrows/WS.png'/> as well as dilation of temporal horn <img src='img/arrows/CO.png'/>.*
![Coronal T2-weighted MR at 3.0T in a patient with prolonged febrile seizure shows abnormal enlargement and T2 hyperintensity in the right hippocampus <img src='img/arrows/CS.png'/>. DWI (not shown) revealed reduced diffusion. The patient later developed HS.](images/app.statdx.com_image_thumbnail_74b0b992-2cdf-45eb-8017-85fc1e87611e_annotated_true_size_900_quality_90_3f5feaac83668e19a878ee41c2e943eecc95b7f7.jpg)
*Coronal T2-weighted MR at 3.0T in a patient with prolonged febrile seizure shows abnormal enlargement and T2 hyperintensity in the right hippocampus <img src='img/arrows/CS.png'/>. DWI (not shown) revealed reduced diffusion. The patient later developed HS.*
![Coronal FLAIR MR in a patient with longstanding partial complex epilepsy shows bilateral hyperintense hippocampi <img src='img/arrows/CC.png'/> with loss of normal architecture, volume loss, R &gt; L, consistent with bilateral mesial temporal sclerosis.](images/app.statdx.com_image_thumbnail_4baba424-f042-4233-9ee7-54e4780a61cf_annotated_true_size_900_quality_90_597f982c61c3d3471423b53cd1b35cf280483532.jpg)
*Coronal FLAIR MR in a patient with longstanding partial complex epilepsy shows bilateral hyperintense hippocampi <img src='img/arrows/CC.png'/> with loss of normal architecture, volume loss, R &gt; L, consistent with bilateral mesial temporal sclerosis.*
![Coronal T2WI MR in a patient with chronic seizures with large right temporal lobe cavernous malformation <img src='img/arrows/CO.png'/> demonstrates all 3 primary determinants of right HS <img src='img/arrows/CC.png'/> (volume loss, T2 hyperintensity, and loss of internal architecture).](images/app.statdx.com_image_thumbnail_7e17968d-3747-4a67-9267-e700cbe7d354_annotated_true_size_900_quality_90_06145e7a230f709c09d1602bd00fa9b5b2d34167.jpg)
*Coronal T2WI MR in a patient with chronic seizures with large right temporal lobe cavernous malformation <img src='img/arrows/CO.png'/> demonstrates all 3 primary determinants of right HS <img src='img/arrows/CC.png'/> (volume loss, T2 hyperintensity, and loss of internal architecture).*
![Coronal FLAIR MR in the same patient with right temporal lobe cavernous malformation <img src='img/arrows/CO.png'/> better shows HS <img src='img/arrows/CS.png'/>. Hyperintensity is usually more conspicuous on FLAIR, while T2 is better for depicting internal structure.](images/app.statdx.com_image_thumbnail_f365f7c5-ef03-453c-ab72-5e5a013fd7ed_annotated_true_size_900_quality_90_7b1eab3ade8a4f5ce6f2d370699340d2a6ad6f24.jpg)
*Coronal FLAIR MR in the same patient with right temporal lobe cavernous malformation <img src='img/arrows/CO.png'/> better shows HS <img src='img/arrows/CS.png'/>. Hyperintensity is usually more conspicuous on FLAIR, while T2 is better for depicting internal structure.*
### Additional Images
![Coronal T2WI MR shows classic left hippocampal sclerosis with abnormal T2 hyperintensity, ipsilateral atrophy, and loss of internal architecture.](images/app.statdx.com_image_thumbnail_20da7e0c-b7da-4c58-948a-a05d30898252_annotated_true_size_900_quality_90_dbd8b754c54d0c28891b2802a0db7fa7f22cc3fc.jpg)
*Coronal T2WI MR shows classic left hippocampal sclerosis with abnormal T2 hyperintensity, ipsilateral atrophy, and loss of internal architecture.*
![Coronal T1WI 3D SPGR demonstrates classic left HS with ipsilateral atrophy and loss of normal internal gray-white differentiation.](images/app.statdx.com_image_thumbnail_e4dae355-94eb-46ee-a004-6593e2f19865_annotated_true_size_900_quality_90_ff9dfb5ce3a2b13cdfba9e269d93851462afd250.jpg)
*Coronal T1WI 3D SPGR demonstrates classic left HS with ipsilateral atrophy and loss of normal internal gray-white differentiation.*
![Coronal FLAIR MR in a patient with complex partial epilepsy with left hippocampal sclerosis shows ipsilateral volume loss and conspicuous hyperintensity resulting from gliosis.](images/app.statdx.com_image_thumbnail_6b2c6161-10e8-48cc-b72f-64be747eecb2_annotated_true_size_900_quality_90_0c6c5bbe354dfdc0d5c6dafef56c39418727d646.jpg)
*Coronal FLAIR MR in a patient with complex partial epilepsy with left hippocampal sclerosis shows ipsilateral volume loss and conspicuous hyperintensity resulting from gliosis.*
![Coronal T2WI MR in a 23 year old with complex partial seizures reveals abnormal hyperintensity and atrophy of the right hippocampus <img src='img/arrows/WS.png'/>. Loss of internal architecture is also seen, typical of MTS.](images/app.statdx.com_image_thumbnail_82bd91b0-0ea8-4335-9c91-07c8748ff073_annotated_true_size_900_quality_90_e12442430b18bfd85385dcd45f2708b57159efce.jpg)
*Coronal T2WI MR in a 23 year old with complex partial seizures reveals abnormal hyperintensity and atrophy of the right hippocampus <img src='img/arrows/WS.png'/>. Loss of internal architecture is also seen, typical of MTS.*
![Coronal T2WI MR shows abnormal hyperintense signal and atrophy of the right anterior temporal lobe related to prior injury.](aa315f34-25ff-4833-a882-aa73bbeece45)
*Coronal T2WI MR shows abnormal hyperintense signal and atrophy of the right anterior temporal lobe related to prior injury.*
![Coronal T2WI MR in a patient with acute complex partial seizures shows abnormal enlargement and hyperintensity of the right hippocampus <img src='img/arrows/BS.png'/>. Follow-up imaging 9 months later (not shown) confirmed subsequent development of right MTS.](75e76424-620b-4878-b335-00ca48858d58)
*Coronal T2WI MR in a patient with acute complex partial seizures shows abnormal enlargement and hyperintensity of the right hippocampus <img src='img/arrows/BS.png'/>. Follow-up imaging 9 months later (not shown) confirmed subsequent development of right MTS.*
![Coronal STIR MR at 3.0T in a normal nonepileptic patient shows a prominent left collateral sulcus <img src='img/arrows/WS.png'/> that changes the morphology of the adjacent normal hippocampus. This common anatomical variant can be mistaken for HS.](c59e6abd-cef6-40e5-8956-b6e0d31a06ec)
*Coronal STIR MR at 3.0T in a normal nonepileptic patient shows a prominent left collateral sulcus <img src='img/arrows/WS.png'/> that changes the morphology of the adjacent normal hippocampus. This common anatomical variant can be mistaken for HS.*
![Coronal STIR MR at 3.0T in an individual who had been born prematurely with developmental delay shows diffuse white matter volume loss (L &gt; R) and concordant left hippocampal volume loss with the abnormal T2 hyperintensity <img src='img/arrows/WS.png'/> of HS.](1b9cc8f7-349a-44c9-b7b6-be26f0f6072a)
*Coronal STIR MR at 3.0T in an individual who had been born prematurely with developmental delay shows diffuse white matter volume loss (L &gt; R) and concordant left hippocampal volume loss with the abnormal T2 hyperintensity <img src='img/arrows/WS.png'/> of HS.*
![Coronal T2WI FS MR in a patient with longstanding partial complex epilepsy shows bilateral shrunken, hyperintense hippocampi <img src='img/arrows/WS.png'/> associated with diminished white matter volume in temporal lobes, consistent with bilateral HS.](ca10ec92-72c0-4b27-87ef-3fca0659c0a0)
*Coronal T2WI FS MR in a patient with longstanding partial complex epilepsy shows bilateral shrunken, hyperintense hippocampi <img src='img/arrows/WS.png'/> associated with diminished white matter volume in temporal lobes, consistent with bilateral HS.*
![Coronal STIR MR at 3.0 T in a normal nonepileptic patient imaged for headaches demonstrates normal bilateral hippocampal anatomy <img src='img/arrows/CC.png'/>, size, and signal intensity.](56e7abb7-09b7-4b92-990b-b4889c385a93)
*Coronal STIR MR at 3.0 T in a normal nonepileptic patient imaged for headaches demonstrates normal bilateral hippocampal anatomy <img src='img/arrows/CC.png'/>, size, and signal intensity.*
![Coronal T2 MR in a patient with epilepsy shows a vertical left collateral sulcus <img src='img/arrows/CS.png'/> and a globular hippocampus <img src='img/arrows/CC.png'/>. This common variation can be mistaken for HS.](49fcab4e-9e3a-4310-a2ef-697a78d2f99d)
*Coronal T2 MR in a patient with epilepsy shows a vertical left collateral sulcus <img src='img/arrows/CS.png'/> and a globular hippocampus <img src='img/arrows/CC.png'/>. This common variation can be mistaken for HS.*
![Coronal T2 MR in a patient with longstanding partial complex epilepsy shows bilateral hyperintense hippocampi <img src='img/arrows/CC.png'/> with volume loss, R &gt; L, consistent with bilateral MTS.](ce5f4cd7-f97e-4b62-baff-1684a6631f09)
*Coronal T2 MR in a patient with longstanding partial complex epilepsy shows bilateral hyperintense hippocampi <img src='img/arrows/CC.png'/> with volume loss, R &gt; L, consistent with bilateral MTS.*