List the systems involved in balance and some of the symptoms that may result if this system is operating less than optimally.

Briefly describe the vestibular apparatus and how its two main components function.

Define dizziness and differentiate it from vertigo and oscillopsia.

List as many causes of dizziness as possible; what is the most serious cause from the PT's perspective?

How may the vestibular system be damaged during whiplash and is the incidence of vestibular disturbance common or uncommon in these patients?

List three ways that you could differentiate neurovascular induced vertigo from vestibular hypofunction vertigo.

The major systems are:

• The vestibular apparatus (semicircular canals, utricle, saccule)
• The direct neural connections (i.e. 8th nerve and vestibular nucleus)
• The neural integrators
• The various vestibular tracts (trigeminal, spinal, ocular, cortical)
• The cerebellum
• The exteroceptors throughout the body but particularly from the upper cervical levels including joints and muscles and the extra-ocular muscle
• The optic nerves and tracts especially from the occipital cortex and the pretectum

Dysfunction of any of these systems could result in types one, two or three dizziness, ataxia, a widened base while walking, nystagmus, drop attacks and/or vomiting.

The vestibular apparatus consists of, the three semicircular canals (the dynamic labyrinth) whose main function is to register changes in angular displacement of the head in relation to the line of gravity, and the utricle and saccule (the static labyrinth) which mainly registers position. They subserve to major reflexes, the vestibulospinal and the vestibulo-ocular.

Dizziness is a sense of imbalance and is a very non-specific term and may include giddiness, wooziness, lightheadedness, nausea, dysequilibrium, fainting or vertigo. Vertigo is an illusion of rotatory motion while oscillopsia is an illusion of linear motion.

Traumatic and non-traumatic vestibular apparatus disorders (will be covered more exhaustively in an upcoming article), neurological diseases such as MS, syphilis, syringobulbia, epilepsy, cerebellar conditions etc., cerebral concussion and contusion, 8th neuromas, brainstem tumors, middle ear infections, vestibular neuronitis, Ramsey-Hunt disease (7th and 8th nerve shingles), metabolic (anemia, diabetes), cardiovascular diseases (dysrythmias, CCF), psychiatric, migraine, fever, hunger, toxins such as alcohol, carbon monoxide, medications (over 400 listed), TMJ problems, cervical joint dysfunction and VBI. Of these VBI is the most threatening to the OMT as tearing or embolus effects of the arterial system may lead to catastrophic consequences for the patient.

The vestibular apparatus appears to be mainly damaged by the hyperextension phase of the whiplash. It can causes displacement of the otoconia into the amupullae (cupulolithiasis) or into the semicircular canal endolymph (canalolithiasis), tearing of the membrane separating the endolymph and the perilymph or tearing of the vestibular membrane (perilymph fistula), tympanic membrane rupture, oscicular fracture and/or dislocation, temporal bone fracture, traumatic inflammation (post-traumatic hydrops). Damage to this system appears to occur relatively commonly. Depending on the article read, the number varies between 25-55% of post-whiplash victims have evidence of vestibular damage.

The presence of neighbourhood brainstem signs such as elements of Wallenberg's or medial meduallary syndrome including, Horner's syndrome, dysphasia, dysarthria, dysphagia, gaze evoked nystagmus, quadra/hemianopia, hemifacial hypo/anasthesia, lingular deviation on protrusion, long tract signs such as pain and temperature sensation loss, vibration sensation loss, past pointing, hyper-reflexia, a Babinski response etc. would all suggest neurovascular causes. The Hallpike-Dix being negative while cervical extension or extension/rotation was positive would suggest neurovasculogenisis. Body rotation negative while cervcial extension or extension/rotation was positive would also suggest VBI. Vertical or purely linear or torionsal nystagmus is indicative of central cause while horizontal and mixed torsional-linear nystagmus suggests a peripheral mechanism. Central vertigo tends to be less severe and does not have a latency nor necessarily a recovery period.