Answer for BIR CoW 09 Jan 2022
Mesial Temporal Sclerosis
Findings
Hippocampal volumetry – - Volumetric analysis of the hippocampal structures on both sides shows significant asymmetric reduction in volume in the right side (Dentate gyrus, cornus ammonis, subiculum, alveus and fimbria were included). - Volume of right hippocampus – 1.8 cc3. - Volume of left hippocampus – 2.9cc3. T2 Relaxometry – - Right hippocampus – 127 - Left hippocampus – 118 IMPRESSION Right Mesial Temporal Sclerosis
Discussion
Mesial temporal sclerosis (MTS) is a specific pattern of hippocampal neuronal loss accompanied by gliosis and atrophy. MTS is the most common cause of partial complex epilepsy in adults and is also the most common etiology in young adult patients undergoing surgery. Coronal T2W and FLAIR images are the most sensitive for detecting MTS. Hippocampal hyperintensity on T2WI or FLAIR images with volume loss (recognised by asymmetry in the case of unilateral atrophy) is diagnostic for mesial temporal sclerosis in the appropriate clinical setting. There are numerous secondary MR features that support the diagnosis of MTS. These include temporal horn dilatation, loss of hippocampal internal architecture, decreased hippocampal signal on T1WI and poor parahippocampal grey-white matter definition. Other findings include ipsilateral atrophy of the temporal lobe, thalamus, fornix and mamillary body. These secondary features are present in 40 - 60% of patients with MTS. On their own, the above signs are unreliable, but in conjunction with the primary findings the diagnostic accuracy is improved. Decreased apparent diffusion coefficient levels may be seen on diffusion-weighted imaging. MR spectroscopy shows reduced N-acetyl aspartate (NAA) levels in the ipsilateral mesial temporal lobe assisting in the lateralisation of temporal lobe epilepsy, even in cases with negative MR images. MR spectroscopy findings typically represent neuronal dysfunction - decreased NAA and decreased NAA/Cho and NAA/Cr ratios, decreased MI in ipsilateral temporal lobe, increased lipid and lactate soon after a seizure episode. MR Perfusion - During the peri-ictal phases, perfusion is increased, not only in the mesial temporal lobe but often in large parts of temporal lobe and hemisphere. In interictal periods, conversely, perfusion is reduced. Relaxometry is measurement of relaxation times from MR images. T2 relaxometry has found useful in quantitating signal changes on T2-weighted images. It may detect subtle pathology, which is useful in lateralizing temporal lobe epilepsy, even in the absence of hippocampal atrophy. There is bilateral involvement in 20% of cases and in these cases MRI-based hippocampal volumetry has been shown to quantitatively indicate the presence of hippocampal volume loss. MRI also provides information on the predictive value concerning neurologic outcome in patients undergoing temporal lobe surgery. MRI can identify hippocampal volume loss and coexisting extrahippocampal lesions which predict an unfavourable postoperative neurocognitive outcome.
REFERENCES
1) Osborn AG, Cooper JA, Castillo M, et al. Diagnostic Imaging – Brain. St Louis: WB Saunders, 2004. 2) Connor EJ, Jarosz JM. Magnetic resonance imaging of patients with epilepsy. Clin Radiol 2001; 56: 787-801. 3) Camacho DL, Castillo M. MR imaging of temporal lobe epilepsy. Semin. Ultrasound CT MR. 2007;28 (6): 424-36 4) Kasasbeh A, Hwang EC, Steger-May K et-al. Association of magnetic resonance imaging identification of mesial temporal sclerosis with pathological diagnosis and surgical outcomes in children following epilepsy surgery. J Neurosurg Pediatr. 2012;9 (5): 552-61
Findings
Hippocampal volumetry – - Volumetric analysis of the hippocampal structures on both sides shows significant asymmetric reduction in volume in the right side (Dentate gyrus, cornus ammonis, subiculum, alveus and fimbria were included). - Volume of right hippocampus – 1.8 cc3. - Volume of left hippocampus – 2.9cc3. T2 Relaxometry – - Right hippocampus – 127 - Left hippocampus – 118 IMPRESSION Right Mesial Temporal Sclerosis
Discussion
Mesial temporal sclerosis (MTS) is a specific pattern of hippocampal neuronal loss accompanied by gliosis and atrophy. MTS is the most common cause of partial complex epilepsy in adults and is also the most common etiology in young adult patients undergoing surgery. Coronal T2W and FLAIR images are the most sensitive for detecting MTS. Hippocampal hyperintensity on T2WI or FLAIR images with volume loss (recognised by asymmetry in the case of unilateral atrophy) is diagnostic for mesial temporal sclerosis in the appropriate clinical setting. There are numerous secondary MR features that support the diagnosis of MTS. These include temporal horn dilatation, loss of hippocampal internal architecture, decreased hippocampal signal on T1WI and poor parahippocampal grey-white matter definition. Other findings include ipsilateral atrophy of the temporal lobe, thalamus, fornix and mamillary body. These secondary features are present in 40 - 60% of patients with MTS. On their own, the above signs are unreliable, but in conjunction with the primary findings the diagnostic accuracy is improved. Decreased apparent diffusion coefficient levels may be seen on diffusion-weighted imaging. MR spectroscopy shows reduced N-acetyl aspartate (NAA) levels in the ipsilateral mesial temporal lobe assisting in the lateralisation of temporal lobe epilepsy, even in cases with negative MR images. MR spectroscopy findings typically represent neuronal dysfunction - decreased NAA and decreased NAA/Cho and NAA/Cr ratios, decreased MI in ipsilateral temporal lobe, increased lipid and lactate soon after a seizure episode. MR Perfusion - During the peri-ictal phases, perfusion is increased, not only in the mesial temporal lobe but often in large parts of temporal lobe and hemisphere. In interictal periods, conversely, perfusion is reduced. Relaxometry is measurement of relaxation times from MR images. T2 relaxometry has found useful in quantitating signal changes on T2-weighted images. It may detect subtle pathology, which is useful in lateralizing temporal lobe epilepsy, even in the absence of hippocampal atrophy. There is bilateral involvement in 20% of cases and in these cases MRI-based hippocampal volumetry has been shown to quantitatively indicate the presence of hippocampal volume loss. MRI also provides information on the predictive value concerning neurologic outcome in patients undergoing temporal lobe surgery. MRI can identify hippocampal volume loss and coexisting extrahippocampal lesions which predict an unfavourable postoperative neurocognitive outcome.
REFERENCES
1) Osborn AG, Cooper JA, Castillo M, et al. Diagnostic Imaging – Brain. St Louis: WB Saunders, 2004. 2) Connor EJ, Jarosz JM. Magnetic resonance imaging of patients with epilepsy. Clin Radiol 2001; 56: 787-801. 3) Camacho DL, Castillo M. MR imaging of temporal lobe epilepsy. Semin. Ultrasound CT MR. 2007;28 (6): 424-36 4) Kasasbeh A, Hwang EC, Steger-May K et-al. Association of magnetic resonance imaging identification of mesial temporal sclerosis with pathological diagnosis and surgical outcomes in children following epilepsy surgery. J Neurosurg Pediatr. 2012;9 (5): 552-61
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!