Lesions of the Archicerebellum and Vermis of the Anterior and Posterior Lobes

The archicerebellum consists of the flocculonodular lobe of which the nodulus is part of the vermis. The remainder of the vermis of the anterior and posterior lobes is closely related to the flocculonodular lobe in that Purkinje cells project to the fastigial nuclei as well as directly to the lateral and other vestibular nuclei; the entire vermis receives input from the vestibular complex.

Lesions of the archicerebellum and other parts of the vermis produce disturbances in stance and gait. The patient stands and walks with feet several inches apart (broad-based gait) and has difficulty in placing the heel of one foot in front of the other in a sequential order (impairment of tandem gait). Titubation, a rapid rhythmic tremor of the head or body, can occur, sometimes accompanied by nystagmus (rhythmic oscillation of the eyes).

Cortical degeneration affecting the vermis of the anterior and posterior lobes is seen in some alcoholic patients. Disturbances involve the lower limbs and gait, which is ataxic and wide based. Asynergia of the lower limbs can be demonstrated by the heel-shin test in which the heel of one foot is made to slide down the shin of the opposite leg.

Lesions involving the flocculonodular lobe and uvula can result in ataxia of the trunk muscles without any signs of tremor or hypotonia. Children with nodular lobe tumors have a tendency to fall backward, sway from side to side, and walk with a wide base and an ataxic gait. They might be unable to maintain an upright balance.

Neurodegenerative Diseases Affecting the Cerebellum

Cerebellar ataxia together with dementia is distinguished by a spongiform degeneration of cortical neurons in the cerebellum and cerebrum. Degeneration coupled with marked glial proliferation cytoplasmic vacuoles is referred to as spongiform. The main clinical signs are cerebellar ataxia and progressive dementia. Diseases expressing these manifestations include Kuru, documented in New Guinea where human brains were eaten while preparing bodies for burial, Creutzfeldt-Jacob disease, shown to be transmittable, scrapie, a disease found in sheep, and mad cow disease. All of these related diseases appear to be caused by modifications of the conformation of proteins called “prions” (Prusiner, 1998).

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  • Category: Nervous diseases