Central pathological causes of vertigo result from dysfunction of the vestibular portion of the VIII nerve, the vestibular nuclei within the brainstem and their central connections. (Table 4):

Neural connections with the central vestibular nuclei include interaction with the vestibular portions of the cerebellum (primarily the cerebellar flocculus); the visual sensory system; and afferent connections from muscle, joint, and tactile receptors. Normal persons will experience physiological vertiginous sensations when visual and vestibular inputs are in conflict or when they are initially exposed to heights. Central pathological causes of vertigo are less common than either peripheral or systemic causes, the vertiginous symptoms are usually less prominent, and additional neurological signs are usually present on examination.

Brainstem Ischemia and Infarction 

The posterior circulation supplies blood to the brainstem, cerebellum, peripheral vestibular apparatus, in addition to other structures. It is not surprising that vertebrobasilar insufficiency may be accompanied by vertigo. In general, brainstem TIAs should be accompanied by neurologic symptoms or signs, in addition to vertigo or dizziness before a clear-cut diagnosis is entertained. However, it is clear that isolated episodes of vertigo lasting many minutes, may be due to posterior circulation dysfunction (Grad and Baloh, 1989, Oas and Baloh, 1992). Symptoms include transient clumsiness, weakness, loss of vision, diplopia, perioral numbness, ataxia, drop attack, and dysarthria (Amarenco, 1991; Caplan 1993). Common signs of vertebrobasilar ischemia include disorders of motor function such as weakness, clumsiness, or paralysis. A crossed defect (a motor or sensory deficit on one side of the face and the opposite side of the body) is good evidence of brainstem dysfunction. If the occipital lobes are the site of ischemia, transient visual loss in the form of complete or partial homonymous hemianopia will occur. Ataxia, imbalance, unsteadiness, or disequilibrium not necessarily associated with spinning vertigo may occur because of labyrinthine or cerebellar ischemia.

However, it is incorrect to believe that dizziness must be present before a TIA of the posterior circulation can be diagnosed. Isolated symptoms like those described may occur without dizziness. On the other hand, it has been overemphasized that such symptoms must always accompany dizziness, when the vertiginous symptoms are due to brainstem TIA. In elderly patients with no laboratory evidence of peripheral vestibulopathy or systemic disease, episodic disequilibration or dizziness may be due to vertebrobasilar disease (Grad and Baloh, 1989).

Sudden hearing loss with moderate dizziness may be due to infarction in the distribution of the internal auditory artery. In isolation, this symptom complex is uncommon in elderly patient with atherosclerotic vertebrobasilar disease, and is more suggestive of diseases affecting small and intermediate-diameter arteries such as syphilis, systemic lupus erythematosus, or periarteritis nodosa. In the atherosclerotic patient, such symptoms are usually accompanied by other signs of brainstem or cerebellar dysfunction, which allow a more certain diagnosis. If actual brainstem infarction occurs, neurological signs are often present on examination. Such signs may not be obvious and should be carefully sought. They include nystagmus of the central type, hyperreflexia, internuclear ophthalmoplegia, homonymous visual field defects, dysarthria, vertebral bruits, and ataxia (Leigh and Zee, 1991). Symptoms of dizziness are also quite common in proximal extracranial occlusion of the vertebral arteries (Caplan 1993) and in the subclavian steal syndrome.

Up to this point, the emphasis has been on the accompanying signs and symptoms that almost always occur with vertebrobasilar disease. It is noteworthy, however, that acute severe vertigo, mimicking labyrinthine disease, is an early symptom of acute cerebellar infarction in the distal territory of the posterior inferior cerebellar artery (Amarenco 1991). To differentiate this condition from labyrinthine disease, particular attention is directed to the type of nystagmus that is present. Acute peripheral vestibulopathy usually causes unidirectional nystagmus, with the fast phase in the opposite direction. This is similar to the mnemonic COWS (Cold, Opposite, Warm, Same) for remembering the direction of the nystagmus fast phase during thermal irrigation of the ear. The fast phase is away from the side of the cold water irrigation. Cold water mimics a peripheral destructive lesion of the labyrinth, and almost all lesions are destructive. Therefore, with a peripheral labyrinthine disturbance, the nystagmus fast phase is in the opposite direction or away from the involved ear. The nystagmus increases during gaze in the direction of the fast phase or contralateral to the peripheral vestibulopathy. Swaying or falling occurs toward the side of the lesion (opposite the nystagmus fast phase). The nystagmus direction is said to be fixed in that it tends to be uni-directional, away from the side of the peripheral vestibulopathy and tends to remain horizontal on upward gaze.

However, in certain syndromes of the posterior circulation, the initial presentation with acute vertigo suggests peripheral vestibulopathy. With incipient cerebellar infarction the sway or fall is toward the side of the lesion. The accompanying nystagmus may be variable in direction but is most prominent during gaze toward the lesion. In other words, with central lesions the fast phase of the nystagmus is in the direction of gaze (direction changing nystagmus) but becomes more prominent when gaze is directed ipsilateral to the lesion (Troost, 1996, Oas and Baloh 1992). Ocular motor findings are often present in brainstem disease, such as limitation of vertical gaze, upbeat or downbeat nystagmus or disconjugate nystagmus.

Multiple Sclerosis 

Multiple sclerosis should only be diagnosed following the documentation of disseminated CNS lesions such as optic neuritis, transverse myelitis, internuclear ophthalmoplegia or other brainstem signs, and MRI changes. Occasionally, signs and symptoms suggestive of multiple sclerosis, including disequilibration and dizziness, may be mimicked by an intrinsic brainstem tumor in a young patient.

Cerebellopontine Angle Tumors 

Tumors of the cerebellopontine angle rarely present solely with episodic vertigo. The most common tumor in this location results from a proliferation of the Schwann cells, hence the name schwannoma. Most of these tumors arise on the vestibular portion of the VIII nerve within the internal auditory canal. They progressively enlarge, deforming the internal auditory meatus and compressing adjacent neural structures such as the acoustic portion of the eighth nerve, facial nerve, trigeminal nerve, brainstem and cerebellum. Other tumors occurring in the cerebellopontine angle include meningiomas, epidermoids and metastases.

The most common symptoms associated with eighth nerve tumors are progressive hearing loss and tinnitus. Vertigo occurs in approximately 20%, but a symptom of imbalance or disequilibration is more common. Rarely a patient with a vestibular nerve tumor may present with subtle hearing loss, tinnitus and episodic vertigo. All those with progressive unilateral hearing loss, and particularly those with any vestibular symptoms should be carefully examined for additional neurological signs such as a depressed corneal reflex.

Cranial Neuropathy 

Systemic disease, including vasculitis, granulomatous disease, and meningeal carcinomatosis. The cause is often elusive. Evidence of systemic involvement is elicited by history, physical examination, and laboratory evaluation. Cogan's syndrome may be considered with cranial neuropathies. The condition is characterized by nonsyphilitic keratitis associated with vertigo, tinnitus, ataxia, nystagmus, rapidly progressive deafness, and systemic involvement.

Posterior Fossa Lesions 

Posterior fossa lesions in a variety of locations are unusual causes of isolated vertigo. The symptoms are usually positional vertigo of the central type (see Table 3). Magnetic resonance imaging (MRI) with coronal and sagittal reconstructions permits identification of small tumors close to the tissue-bone interface, a region often blurred by bone artifact in CT scans.

Acquired disease of the brainstem and cerebellum produces a variety of types of nystagmus, which sometimes present as a complaint of oscillopsia, an illusion of environmental movement characterized by bouncing or jiggling of objects. Although oscillopsia is a common complaint with bilaterally reduced vestibular function as from ototoxicity, the presence of vertical oscillopsia should alert the physician to look for primary position upbeat or downbeat nystagmus. These nystagmus types are reliable indicators of CNS abnormality due to structural intrinsic midline cerebellar disease or drugs.

Seizure Disorders 

Seizure disorders, especially complex partial epilepsy, are rare causes of dizziness or vertigo. The history almost always reveals additional symptoms such as loss of awareness, automatic behavior, or generalized seizure activity following an aura of vertigo. Rare seizure patients have isolated auras of the symptoms listed in Table 1 including spinning vertigo.