Central pontine and extrapontine myelinolysis: the osmotic demyelination syndromes

Central pontine myelinolysis (CPM) was described by Adams and colleagues in 1959 as a disease affecting alcoholics and the malnourished.1 The concept was extended from 1962 with the recognition that lesions can occur outside the pons, so-called extrapontine myelinolysis (EPM). In 1976 a link between these disorders and the rapid correction of sodium in hyponatraemic patients was suggested, and by 1982 substantially established. In this review we discuss the clinical, pathological, and aetiological features of the disease, the dilemma facing clinicians treating patients with severe hyponatraemia, and treatment opportunities.

OSMOTIC DEMYELINATION SYNDROMES: CPM AND EPM

Clinical manifestations

Central pontine myelinolysis (CPM)

Nothing has been added to the clinical description of CPM since the original report. The patient has usually gone through a biphasic clinical course, initially encephalopathic or presenting with seizures from hyponatraemia, then recovering rapidly as normonatraemia is restored, only to deteriorate several days later. The initial signs of the CPM, which reflect this second phase, include dysarthria and dysphagia (secondary to corticobulbar fibre involvement), a flaccid quadriparesis (from corticospinal tract involvement) which later becomes spastic, all from involvement of the basis pontis (fig 1); if the lesion extends into the tegmentum of the pons pupillary, oculomotor abnormalities may occur. There may be an apparent change in conscious level reflecting the “locked-in syndrome” that a large lesion in this site is particularly liable to produce. If lesions of EPM are also present the clinical picture may be very confusing, as added to the above, or even preceding, can be a variety of apparently psychiatric and behavioural changes and movement disorders (outlined below).

To summarise: “…whenever a patient who is gravely ill with alcoholism and malnutrition or …