Herniation of cerebellar tonsils in acromegaly: prevalence, pathogenesis and clinical impact.

Herniation of cerebellar tonsils (CTH) might occur in acromegaly patients and improve after acromegaly treatment. Our study investigated CTH prevalence in acromegaly, its relationship with clinical, laboratory and neuroimaging findings and its possible pathogenesis and clinical impact. 150 acromegaly patients (median-age 56 years, age-range 21-88, 83 females) underwent brain magnetic resonance imaging (MRI). Clinical data, laboratory and pituitary adenoma imaging findings were recorded. CTH, posterior cranial fossa area, tentorial angle, clivus, supraocciput and Twining's line length were measured in acromegaly patients and controls, who included MRI of 115 consecutive subjects with headache or transient neurological deficits (control group-1) and 24 symptomatic classic Chiari 1 malformation patients (control group-2). Acromegaly patients were interviewed for symptoms known to be related with CTH. 22/150 acromegaly patients (15 %) and 8/115 control group-1 subjects presented with CTH (p = 0.04). In acromegaly patients, CTH correlated positively with younger age and inversely with GH-receptor antagonist treatment. Control group-2 had a shorter clivus than CTH acromegaly patients (40.4 ± 3.2 mm vs 42.5 ± 3.3 mm, p < 0.05), while posterior fossa measures did not differ among acromegaly subgroups (with and without CTH) and control group-1. Headache and vision problems were more frequent in CTH acromegaly patients (p < 0.05); two acromegaly patients presented with imaging and neurological signs of syringomyelia. Despite no signs of posterior fossa underdevelopment or cranial constriction, CTH is more frequent in acromegaly patients and seems to contribute to some disabling neurological symptoms.