MRI-negative cerebellar syndrome caused by medication-induced magnesium deficiency: a case report

Cerebellar pathologies in adults can have a wide range of hereditary, acquired and sporadic-degenerative causes. Due to the frequency in daily hospital, especially intensive care, settings, electrolyte imbalances are an important, yet rare differential diagnosis. The hypomagnesemia-induced cerebellar syndrome (HiCS) constitutes a relevant disease entity with clinical and morphological variability due to a potential progression of symptoms and a promising causal treatment. Cases of HiCS without imaging abnormalities are scarcely reported and pose a particular challenge to practitioners.

A 68-year-old female patient presented with subacute onset gait impairment and concomitant vertigo. Gaze induced nystagmus, ataxia and limb dysmetria became objectifiable. A broad diagnostic workup, including liquor puncture, whole-body positron emission tomography, antibody serology and most notably thin-layer magnetic resonance imaging remained unconclusive. Only a more detailed examination of chronic hypokalemia with the detection of severe magnesium deficiency under the intake of proton pump inhibitors and a recent gastrointestinal infection found a causal treatment through electrolyte substitution.

Electrolyte disorders as a reason for central nervous pathologies remain underdiagnosed and underestimated, as a heterogeneous clinical appearance, the growing number of defined cerebellar diseases and, like in our case, lacking imaging abnormality aggravatingly contrast with a high intake prevalence of triggering medication. The presence of diarrhea or vomiting, electrolyte shortage, cardiac arrhythmia, alcoholism and particularly the intake of proton pump inhibitors in patients with cerebellar symptoms should result in thorough electrolyte diagnostics. Early recognition of this causally treatable cerebellar syndrome and prompt discontinuation of triggering medication are crucial to improve the often poor prognosis.