Dizziness and vertigo in vertebrobasilar disease. Part II. Central causes and vertebrobasilar disease.

Dysfunction of the vestibular portion of the eighth nerve and the vestibular nuclei within the brainstem and their central connections is a central cause of dizziness and vertigo. Neural connections with the central vestibular nuclei include interaction with the vestibular portions of the cerebellum (primarily cerebellar flocculus), the visual sensory system, and afferent connections from muscle, joint, and tactile receptors. Central causes of vertigo are less common than peripheral or "systemic" etiologies, the vertiginous symptomatology is usually less prominent, and additional neurological signs are usually present on examination. Central disorders include demyelinating disease, tumors, seizures, and vertebrobasilar artery disease (table). Demyelinating disease should only be diagnosed after documentation of disseminated central nervous system lesions, such as optic neuritis, transverse myelitis, internuclear ophthalmoplegia, or other focal signs. Cerebellopontine angle tumors do not usually present symptoms of episodic vertigo alone. The most common tumor in this location results from a proliferation of the Schwann cells (which produce the myelin of nerves), hence the name Schwannoma. Most of these tumors arise in the vestibular portion of the eighth nerve within the internal auditory canal. They progressively enlarge, deforming the internal auditory meatus and compressing adjacent neural structures: the acoustic portion of the eighth nerve, facial nerve, root of the trigeminal nerve, brainstem, and