Because ongoing or episodic conditions accompanied by vertigo, unsteadiness, or presyncope are produced by multiple and often subtle causes, it is not surprising that a significant number of patients cannot be readily diagnosed. A major differential diagnostic classification would include broad categories such as (1) peripheral vestibulopathy, (2) central neurological disorders, and (3) systemic or medical conditions. There is some ambiguity in the use of the term central, which has been used by otolaryngologists to include causes that are central or proximal to the vestibular end organ and therefore include the vestibular portion of the eight nerve. Neurologists, however, consider conditions that affect the vestibular nerve, such as tumors, as peripheral in location because they are on a cranial nerve and are extra-axial. Because masses or neoplasms can enlarge to involve other structures in the cerebellopontine angle, particularly the brainstem, conditions that affect the VIII nerve are discussed for convenience in the central category.

PERIPHERAL CAUSES 

Peripheral causes result from dysfunction of vestibular end organs (semicircular canals, utricle, and saccule) (Table 2):

Peripheral Vestibulopathy

Peripheral vestibulopathy, encompasses terms such as vestibular neuronitis, labyrinthitis and viral neurolabyrinthitis. Such terms imply an inflammatory mechanism, which is unproved. Vestibular neuronitis, strictly speaking, is characterized by single or recurrent sudden episodes of true vertigo lasting from hours to days and often associated initially with vomiting. When the condition is associated with hearing loss, the entire labyrinth is assumed to be involved, and the term labyrinthitis is used. Despite this technical distinction, many neuro-otologists, otologists, and neurologists use the terms vestibular neuronitis and labyrinthitis interchangeably, whether or not auditory symptoms are present. In such patients the vertiginous sensation may be provoked by head movement, but not necessarily by a particular head position. Whether isolated viral involvement of the vestibular nerves is a cause of acute or episodic vertigo is controversial. Many prefer the term acute or recurrent peripheral vestibulopathy. In the acute phase, many patients present with sudden severe vertigo, nausea, and vomiting without any hearing disturbance or facial weakness. The acute symptoms usually resolve in a few days to a week, but may recur in weeks or months. If true vertigo is part of the symptom complex, the condition is most likely to be associated with some disorder of the peripheral end organ. However, patients with either acute peripheral vestibulopathy or, more commonly, recurrent attacks may experience only a sensation of lightheadedness or floating, or a feeling of "walking on tennis balls." Even if the patient has had hundreds of episodes, it is important to determine whether any of them were associated with spinning vertigo. Over time, the nature of the patient's symptom complex may change, even with peripheral vestibulopathy, from vertiginous sensations to those of pure unsteadiness or disequilibration.

Epidemic and seasonal outbreaks of acute vertigo have suggested an infectious origin due to viral disease, but this largely remains unproved. Viral labyrinthitis can also be part of a systemic viral infection such as mumps, measles, infectious mononucleosis, or upper respiratory tract viral infections. Isolated viral infections of the labyrinth are also believed to cause the sudden onset of hearing loss and/or vertigo in both children and adults. Otitic Herpes zoster is an infection characterized by pain in the ear, followed in 1 to 10 days by a vesicular eruption in the external ear. When the VIII and VII nerves are affected, there is a combination of facial weakness, hearing loss, and vertigo known as the Ramsay Hunt syndrome. Whenever vertigo is associated with severe ear pain or facial pain, one must consider this possibility. A dysesthetic area of skin may precede, by many days, the appearance of the skin eruption.

Benign Positional Vertigo 

Benign positional vertigo refers to a symptom complex classically described as indicative of benign peripheral (end organ) disease. These symptoms, differentiated from central neurological symptoms, are outlined in Table 3.

The signs and symptoms of benign positional vertigo are transient and rarely last longer than 40 seconds. They frequently occur when a certain position is assumed, such as lying down or turning in bed. Other causes of vertigo are also intensified by position change. Depending on whether the symptom (vertigo) or sign (nystagmus) is being emphasized, this condition is termed paroxysmal postional vertigo (BPPV) or benign paroxysmal positional nystagmus (BPPN). In a major review of 240 cases, Baloh and associates described the clinical and eye movement recording features in patients with BPPV. In each case, after a rapid position change from the sitting to head-hanging position, a stereotyped torsional paroxysmal nystagmus was observed. The time to the onset of the nystagmus, the latency, was from 0 to 40 seconds, with an average of approximately 8 seconds. The initial phase of the nystagmus was rotary and upward, with the upper pole of the eye beating toward the ground on visual inspection. From the examiner's observation the nystagmus should appear counterclockwise, with the left ear down. The average age of onset was 54 years and the most common identifiable causes were head trauma (17%) and viral neurolabyrinthitis (15%).

Troost and Patton (1992) described historical factors which should lead to the consideration of BPPV: (1) symptoms associated with certain head positions, (2) rotational vertigo, episodic in nature, (3) antecedent episode of severe rotary vertigo with or without nausea and vomiting associated with upper respiratory infection that suggests prior viral neurolabyrinthitis, (4) history of head trauma before attacks of vertigo, (5) most severe symptomatology early in the day with lessening symptoms as the day progresses, and (6) relative absence of spontaneous symptoms without head movement or positional change. Physical examination findings include (1) vertical-rotary benign positional paroxysmal nystagmus (BPPN) produced by provocative maneuvers. (Figure 3):

Figure 3. Provocative maneuvers for positional vertigo and nystagmus. The patient is abruptly moved from a seated position to one with the head hanging 45 degrees below the horizontal and rotated 45 degrees to one side. He or she is then observed for positional nystagmus. The maneuvers are repeated with the head straight back and turned to the other side.

(2) latency to onset of symptoms once precipitating head position is achieved, (3) short-duration nystagmus (3 to 30 seconds), and (4) adaptation of nystagmus and symptoms--i.e., disappeance with repeated maneuvers. An additional feature of the physical examination is that BPPN is not a constant feature, being present on some examinations but absent at other times. The finding of the typical nystagmus upon assumption of certain head postures is considered the single most important physical finding in making the diagnosis of BPPV. The nystagmus or ocular oscillation is depicted in Figure 4:

Figure 4 In benign paroxysmal positional nystagmus (BPPN), the nystagmus fast phase is horizontal-rotary directed toward the undermost ear when gaze is directed toward the undermost ear (upper panel). The nystagmus fast phase is upward toward the forehead when gaze is directed to the uppermost ear (middle panel). With the eyes in the central orbital position, the nystagmus fast phase is vertical upward and rotary toward the down ear (bottom panel).

Mechanism of BPPV 

It is believed that the short, usually intense, episodes of vertigo and nystagmus are caused by two mechanisms:
(1) Cupulolithiasis: a dislocation of the calcium carbonate crystals which rest on the hair cells of the saccule and utricle of the inner ear which make them susceptible to the pull of gravity. These "ear stones" or otoliths become dislodged due to trauma, prior infection (neurolabyrinthitis or "vestibular neuronitis"), as a normal part of the aging process in 80% of people living between 60 and 80 and just by chance. The otoliths usually settle on the active part of the posterior semicircular canal and convert the receptor from one sensitive to acceleration to one sensitive to position and changing of position. The concept of Cupulolithiasis is bolstered by some histopathology. It is depicted in the following diagram:

The otolith (red, in the insert) has located to the top of a hair cell in the cupula. Exercise therapy is used to move it and eliminate the condition (see treatment section).
(2) Canalithiasis: Otoliths or "dense bodies" become located in the canal itself near the cupula, again in a position to cause symptoms with change in head position. Canalithiasis is depicted in the following diagram:

The dense bodies (violet) or otoliths (blue squares [depending on your viewer]) are lodged near the cupula. A series of head position changes can move the material to a non-sensitive portion of the inner ear (see treatment section).