Year : 2007 | Volume
: 10 | Issue : 2 | Page : 112--114
Ataxic form of central pontine myelinolysis
A Somarajan1, M Baby Paul2, KA Kabeer1, SK Krishnapriyam2,
1 Department of Neurology, Medical College, Thiruvananthapuram, Kerala, India
2 Department of Internal Medicine, Medical College, Thiruvananthapuram, Kerala, India
Department of Neurology, Medical College, Thiruvananthapuram, Kerala
Central pontine myelinolysis (CPM), a neurologic disorder caused most frequently by rapid correction of hyponatremia, is characterized by demyelination that affects the central portion of the base of the pons. Central pontine myelinolysis occurs frequently in alcoholism and chronic liver disease. Clinical features usually reflect damage to the descending motor tracts and include spastic tetraparesis, pseudobulbar paralysis and the locked-in syndrome. Cerebellar ataxia with out weakness and pyramidal signs is extremely unusual. There are only very few reports of central pontine myelinolysis presenting as cerebellar ataxia.
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Somarajan A, Paul M B, Kabeer K A, Krishnapriyam S K. Ataxic form of central pontine myelinolysis.Ann Indian Acad Neurol 2007;10:112-114
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Somarajan A, Paul M B, Kabeer K A, Krishnapriyam S K. Ataxic form of central pontine myelinolysis. Ann Indian Acad Neurol [serial online] 2007 [cited 2020 Sep 21 ];10:112-114
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In Adams et al described central pontine myelinolysis, a new clinicopathological syndrome characterized by quadriparesis, pseudobulbar palsy and symmetric lesion in centre of basis pontis. Signs of myelinolysis in order of frequency are spastic quadriparesis, pseudobulbar palsy, diminished level of consciousness, behavioral changes, twitching, tremor, papillary abnormalities, facial weakness, incontinence, ataxia, sixth nerve palsy and movement disorders. Myelinolysis can follow a rise in serum sodium from hyponatremic levels regardless of the cause of hyponatremia or method of correction. As myelinolysis occurs not only in pons it is better called Osmotic Dysmyelination syndrome. Unusual clinical presentations include extra pyramidal syndromes, ataxia, catatonia and neurobehavioral syndromes. There are only very few reports of central pontine myelinolysis presenting as cerebellar ataxia.,,,, and none from this subcontinent.
A 54-year-old ex service man with 10-year history of diabetes mellitus and hypertension, six-month history of alcoholic cirrhosis with portal hypertension was admitted with difficulty in walking, dysarthria and diplopia of four days duration. He had his last drink one month back. There was no h/o headache, vomiting, seizures, visual loss, dysphagia, nasal regurgitation, weakness or sensory symptoms. One week back he had cough with acute confusional state and incontinence for two days for which he was admitted in a local hospital. It was not associated with any fever. With the onset of ataxia and diplopia he was referred to our institution. Treatment details from previous hospital were not available.
General examination showed well-built and moderately nourished man with pallor, hepatosplenomegaly and mild ascites. He was afebrile and vitals were normal.
Neurological examination showed an alert person with normal cognition. He had mild esotropia of left eye, minimal movements of eye in horizontal plane with normal vertical movements and intact doll's eye movement in both planes. There was no ocular bobbing or nystagmus. There was no facial weakness. There was mild slurring of speech. Other cranial nerves were normal. There was no weakness. There was hypotonia in limbs with areflexia in lower limbs and normal deep tendon reflexes in upper limbs. There was appendicular ataxia in all limbs with gait ataxia. Sensory examination was normal. There was no flapping tremor or meningeal signs.
Investigations revealed hyperglycemia and deranged liver function tests [Table 1]. Serum sodium was repeatedly low. Lumbar CSF was normal. Following investigations were normal or negative-Thyroid function test, HIV, HBsAg, Anti HCV. Ultrasound abdomen showed hepatosplenomegaly, prominent portal vein and ascites. Upper GI endoscopy showed grade III esophageal varices. Echocardiography showed mild pulmonary hypertension and mild tricuspid regurgitation. CT Head was normal. T2 weighted MRI showed hyper intense lesions in central part of pons, symmetrical hyperintensities of caudate and lentiform nucleus and few subcortical lesions. Diffusion weighted images showed restricted diffusion in central pons. There was no contrast enhancement [Figure 1],[Figure 2].
Clinical differential diagnosis in this case were 1) Recovering Wernicke's encephalopathy) Acute disseminated encephalomyelitis. Even though he had areflexia, ataxia and ophthalmoplegia, supranuclear nature of ophthalmoplegia excluded Miller Fisher syndrome. Radiological differential diagnoses were 1) Central pontine myelinolysis 2) Acute disseminated encephalomyelitis. Preceding hyponatremia, classical central pontine location, bilateral symmetrical basal ganglia involvement favoured central pontine- extrapontine myelinolysis (osmotic dysmyelination syndrome). Imaging features were not suggestive of Wernicke's encephalopathy which usually shows symmetrical hyperintense lesions within the dorsomedial thalami, periaqueductal white matter, the tectum of the midbrain and mamillary bodies. Hyperintense lesions in pons with no restriction of diffusion has been described with hypertensive brainstem encephalopathy.
The prominent cerebellar signs in our patient in the absence of lesions in the cerebellar hemispheres or peduncles indicate involvement of the pontocerebellar fibers, which traverse the base of the pons as they travel from the nuclei pontis to the middle cerebellar peduncles. Pontocerebellar fibers may be more susceptible to the effects of myelinolysis and that in severe cases involvement of the corticospinal fibers masks the cerebellar signs because of the associated weakness. The presence of intact Doll's eye movement indicates either involvement of fibers to paramedian pontine reticular formation (PPRF) from the frontal eye field or PPRF itself and diplopia is probably due to minimal abducent fascicular involvement. Lower limb areflexia is probably due to peripheral neuropathy related to long-standing diabetes and alcoholism.
Our patient had hyponatremia, which was not corrected and still developed myelinolysis. It has been shown that myelinolysis can follow a rise in serum sodium from a hyponatremic levels regardless of the cause of hyponatremia or method of correction. Osmotic Dysmyelination syndrome should be considered in the differential diagnosis of acute cerebellar ataxia even in absence of spastic tetraparesis, pseudobulbar paralysis and the locked-in syndrome especially if there is documented hyponatremia.
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