alcoholic cerebellar degeneration

**Definition:** Chronic, usually subacute-to-insidious cerebellar syndrome in people with long-standing heavy alcohol use and malnutrition. It is one of the most common acquired cerebellar degenerations.

**Pathophysiology:** - Selective atrophy of the anterior and superior cerebellar vermis (the leg and trunk area) and, to a lesser extent, the anterior lobe of the cerebellar hemispheres. - Loss of Purkinje cells, with secondary loss of granule cells and molecular layer thinning. Bergmann gliosis is also seen. - Mechanisms: direct ethanol neurotoxicity (glutamate excitotoxicity during withdrawal, oxidative stress) and thiamine (B1) deficiency from poor intake, reduced GI absorption, and impaired hepatic storage and activation. The same thiamine deficiency causes Wernicke encephalopathy, and the two conditions often coexist. - Vermian predilection explains the clinical pattern: the vermis controls midline structures (trunk, gait, and posture).

**Clinical features:** - Wide-based, unsteady (ataxic) gait. This is the dominant and often only finding, and patients cannot tandem walk. - Truncal ataxia. - Leg incoordination (a heel-to-shin abnormality) is typically worse than arm incoordination. - Relative sparing of limb dysmetria in the arms, dysarthria, and nystagmus. Nystagmus and dysarthria are less prominent than in other cerebellar diseases, but they can occur. - It evolves over weeks to months and may stabilize with abstinence and nutritional repletion. - Frequently coexists with peripheral neuropathy, which can worsen the gait through sensory ataxia.

**Diagnosis:** - Clinical, based on history of chronic alcohol use plus the characteristic gait ataxia. - MRI shows atrophy of the superior vermis. Wernicke-related lesions may appear in the mammillary bodies, medial thalami, and periaqueductal gray. - Exclude other causes of ataxia: B12 deficiency, hypothyroidism, vitamin E deficiency, medications (phenytoin, lithium), paraneoplastic cerebellar degeneration (anti-Yo/anti-Hu), and structural lesions.

**Management:** - Alcohol abstinence. - Thiamine, given before glucose in at-risk patients, plus a nutritional and multivitamin repletion. - Physical therapy and gait training. - Improvement is possible, but it is often incomplete if Purkinje cell loss is established.

**High-yield board associations:** - Alcohol use + wide-based gait + vermian atrophy = alcoholic cerebellar degeneration. - Midline (vermis) lesions cause truncal and gait ataxia. Lateral (hemisphere) lesions cause ipsilateral limb ataxia, dysmetria, and intention tremor. - Wernicke encephalopathy = confusion, ophthalmoplegia/nystagmus, and ataxia (thiamine deficiency). Korsakoff syndrome = anterograde and retrograde amnesia with confabulation (mammillary body and dorsomedial thalamic damage). - Other alcohol-related neurologic conditions: peripheral neuropathy, Marchiafava-Bignami disease (corpus callosum degeneration), central pontine myelinolysis (rapid sodium correction), and alcoholic myopathy. - Other causes of Purkinje cell loss: paraneoplastic syndromes (anti-Yo, ovarian/breast cancer), phenytoin toxicity, and some spinocerebellar ataxias.