Answer for CoW 21 Jan 2018
Osmotic demyelination syndrome
Findings
T2 FLAIR hyperintensity noted in the central pons which shows diffusion restriction sparing peripheral pons, corticospinal tracts and transverse pontine fibres Suggestive of Osmotic pontine demyeliation DD – Pontine infarct
Discussion
Formerly called central pontine myelinolysis and/or extrapontine myelinolysis ODS classically occurs when wide fluxes in serum sodium levels are induced by too rapid correction of hyponatremia Oligodendrocytes are particularly vulnerable to osmotic changes Primarily a pontine lesion; Multifocal involvement is common 50% : isolated pontine lesions. 30% : Myelinolytic foci occur both outside and inside the pons - basal ganglia and hemispheres 20-25% : exclusively extrapontine Other parts involved : cerebellum (especially the middle cerebellar peduncles), basal ganglia, thalami, lateral geniculate body, hemispheric WM and the cortex. Most common in middle-aged patients Most common causes : rapid correction of hyponatremia, alcoholism, liver transplantation, and malnutrition Comorbid conditions that predispose to ODS : renal, adrenal, pituitary, and paraneoplastic disease. Prolonged vomiting (e.g., hyperemesis gravidarum), severe burns, transplants, and prolonged diuretic use Most common presenting symptoms : altered mental status and seizures Other findings include pseudobulbar palsy, dysarthria, and dysphagia. Movement disorders are common when myelinolysis involves the basal ganglia. Outcome varies significantly : complete recovery to coma and death, minimal or no residual deficits, quadriparetic and "locked in." TREATMENT OPTIONS Initial serum sodium is usually under 115-120 mmol/L and serum osmolality less than 275 mOsm/kg Correction of more than 12 mmol/L/day seems to increase the risk of ODS. ODS may also occur in normonatremic patients and independent of changes in serum sodium IMAGING Imaging findings typically lag one or two weeks behind clinical symptoms. NECT : normal or show hypodensity in the central pons MR FINDINGS Standard MR sequences may be normal in the first several days. hypointense on T1WI and hyperintense on T2/FLAIR well-demarcated and symmetric Pontine ODS : round, triangular, or "bat wing"-shaped. The peripheral pons as well as the corticospinal tracts and transverse pontine fibers are spared Basal ganglia and hemispheric WM involved in at least 50%. T2* (GRE, SWI) : no evidence of hemorrhage Late acute or subacute ODS lesions may demonstrate moderate confluent enhancement DWI : most sensitive sequence and can demonstrate restricted diffusion when other sequences are normal DTI : disruption of central pontine WM with sparing of peripheral, transverse tracts Differential Diagnosis Basilar perforating artery infarcts : involve the surface of the pons and are usually asymmetric. Demyelinating disease : can involve the pons but is rarely symmetric. Sagittal FLAIR scans usually demonstrate lesions elsewhere, especially along the callososeptal interface. Pontine gliomas : can expand the pons and appear hyperintense on T2/FLAIR scans. They are neoplasms of children and young adults. The major differential diagnosis of extrapontine ODS with basal ganglia and/or cortical involvement is metabolic disease. Hypertensive encephalopathy (PRES) can involve the pons but does not spare the peripheral WM tracts. Basal ganglia are affected in both Wilson disease and mitochondrial disorders, but the pons is less commonly involved. REFERENCES Osborns Brain Imaging, Pathology and Anatomy 2nd Edition
Findings
T2 FLAIR hyperintensity noted in the central pons which shows diffusion restriction sparing peripheral pons, corticospinal tracts and transverse pontine fibres Suggestive of Osmotic pontine demyeliation DD – Pontine infarct
Discussion
Formerly called central pontine myelinolysis and/or extrapontine myelinolysis ODS classically occurs when wide fluxes in serum sodium levels are induced by too rapid correction of hyponatremia Oligodendrocytes are particularly vulnerable to osmotic changes Primarily a pontine lesion; Multifocal involvement is common 50% : isolated pontine lesions. 30% : Myelinolytic foci occur both outside and inside the pons - basal ganglia and hemispheres 20-25% : exclusively extrapontine Other parts involved : cerebellum (especially the middle cerebellar peduncles), basal ganglia, thalami, lateral geniculate body, hemispheric WM and the cortex. Most common in middle-aged patients Most common causes : rapid correction of hyponatremia, alcoholism, liver transplantation, and malnutrition Comorbid conditions that predispose to ODS : renal, adrenal, pituitary, and paraneoplastic disease. Prolonged vomiting (e.g., hyperemesis gravidarum), severe burns, transplants, and prolonged diuretic use Most common presenting symptoms : altered mental status and seizures Other findings include pseudobulbar palsy, dysarthria, and dysphagia. Movement disorders are common when myelinolysis involves the basal ganglia. Outcome varies significantly : complete recovery to coma and death, minimal or no residual deficits, quadriparetic and "locked in." TREATMENT OPTIONS Initial serum sodium is usually under 115-120 mmol/L and serum osmolality less than 275 mOsm/kg Correction of more than 12 mmol/L/day seems to increase the risk of ODS. ODS may also occur in normonatremic patients and independent of changes in serum sodium IMAGING Imaging findings typically lag one or two weeks behind clinical symptoms. NECT : normal or show hypodensity in the central pons MR FINDINGS Standard MR sequences may be normal in the first several days. hypointense on T1WI and hyperintense on T2/FLAIR well-demarcated and symmetric Pontine ODS : round, triangular, or "bat wing"-shaped. The peripheral pons as well as the corticospinal tracts and transverse pontine fibers are spared Basal ganglia and hemispheric WM involved in at least 50%. T2* (GRE, SWI) : no evidence of hemorrhage Late acute or subacute ODS lesions may demonstrate moderate confluent enhancement DWI : most sensitive sequence and can demonstrate restricted diffusion when other sequences are normal DTI : disruption of central pontine WM with sparing of peripheral, transverse tracts Differential Diagnosis Basilar perforating artery infarcts : involve the surface of the pons and are usually asymmetric. Demyelinating disease : can involve the pons but is rarely symmetric. Sagittal FLAIR scans usually demonstrate lesions elsewhere, especially along the callososeptal interface. Pontine gliomas : can expand the pons and appear hyperintense on T2/FLAIR scans. They are neoplasms of children and young adults. The major differential diagnosis of extrapontine ODS with basal ganglia and/or cortical involvement is metabolic disease. Hypertensive encephalopathy (PRES) can involve the pons but does not spare the peripheral WM tracts. Basal ganglia are affected in both Wilson disease and mitochondrial disorders, but the pons is less commonly involved. REFERENCES Osborns Brain Imaging, Pathology and Anatomy 2nd Edition
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!