SUMMARYPurpose: Research indicates that patients with chronic temporal lobe epilepsy (TLE) exhibit cerebellar atrophy compared to healthy controls, but the degree to which specific regions of the cerebellum are affected remains unclear. The purpose of this study was to characterize the extent and lateralization of atrophy in individual cerebellar lobes and subregions in unilateral TLE using advanced quantitative magnetic resonance imaging (MRI) techniques. Methods: Study participants were 46 persons with TLE and 31 age-and gender-matched healthy controls. All participants underwent high-resolution MRI with manual tracing of the cerebellum yielding gray and white matter volumes of the right and left anterior lobes, superior posterior lobes, inferior posterior lobes, and corpus medullare. The degree to which asymmetric versus generalized abnormalities was evident in unilateral chronic TLE was determined and related to selected clinical seizure features (age of onset, duration of disorder).Key Findings: There were no lateralized abnormalities in cerebellar gray matter or white matter in patients with right or left TLE (all p's > 0.2). Compared with controls, unilateral TLE was associated with significant bilateral reductions in the superior (p = 0.032) and inferior (p = 0.023) posterior lobes, whereas volume was significantly increased in the anterior lobes (p = 0.002), especially in patients with early onset TLE, and not significantly different in the corpus medullare (p = 0.71). Total superior cerebellar tissue volumes were reduced in association with increasing duration of epilepsy. Significance: Patients with unilateral TLE exhibit a pattern of bilateral cerebellar pathology characterized by atrophy of the superior and inferior posterior lobes, hypertrophy of the anterior lobe, and no effect on the corpus medullare. Cross-sectional analyses show that specific aspects of cerebellar pathology are associated with neurodevelopmental (anterior lobe) or chronicity-related (superior posterior lobe) features of the disorder.

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The authors examined a cognitive function mediated by the cerebellum, classical eyeblink conditioning, and its relationship to cerebellar volume in healthy controls (n = 59) and temporal lobe epilepsy subjects (n = 77). Controls demonstrated better conditioning, larger cerebellar volumes, and an association between conditioning and cerebellar volume that was not observed in epilepsy patients. These findings provide support for the hypothesis that cerebellar atrophy in epilepsy affects procedural memory.