Dizziness

=Objectives= These objectives are student defined.

What are the components of balance and causes of dizziness?

 * Balance is coordinated with input and crosstalk between: eyes, ears, musculoskeletal, brainstem, cerebellum and the cerebral cortex.
 * Ear: BPPV, SSCD, Meniere's disease, vestibular neuritis, labyrinthitis, or an acoutic neuroma.
 * Brain: CVA, seizure, migraine, Multiple Sclerosis, Parkinson's, or tumor
 * Medication: hypotension, arrhythmia, and medication side effects
 * Psychiatric: anxiety, panic attack, phobias, hyperventilation, malingering
 * Other: Post concussion and cervical vertigo

Review semicircular canal anatomy and how it contributes to balance

 * Anatomy - courtesy of Purves and wikipedia ;-)
 * These are three half-circular, interconnected tubes located inside of each ear.
 * The horizontal canal is aligned roughly horizontal in the head. The superior and anterior canals are aligned roughly at a 45 degree angle to a plane drawn from the nose to the back of the skull.  Thus, the horizontal canal detects horizontal head movements (doing a pirouette), while the superior and posterior canals detect vertical movements.
 * Each canal has at its base a bulbous expansion called the ampula which houses sensory epithelium, or crista, that contains hair cells.
 * The hair bundles out of the crista into a gelatinous mass, the cupula. Each canal is filled with endolymph.  As the skull twists in any direction, the endolymph is thrown into different sections of the canals.  The cilia detect when the endolymph rushes past because the compliant cupula is distorted.
 * Each semicircular canal works with a partner on the other side of the head. There are three pairs: the two horizontal canals, and the superior canal on each side with the posterior canal on the other side.  Head rotation deforms the cupula in opposing directions for the two partners, resulting in opposite changes in their firing rates.
 * The otolith organs, the utricle and the saccula, are responsible for detecting displacements and linear accelerations of the head.
 * Both contain a sensory epithelium, the macula, which consists of hair cells and associated supporting cells. Overlying the hair cells and their bundles is a gelatinous layer, and above this a fibruous structure, the otolithic membrane, in which are embedded crystals of calcium carbonate called otoconia.
 * The otoconia make the otolithic membrane considerable heavier than the structures and fluids around it; thus, when the head tilts, gravity causes the membrane to shift relative to the sensory epithelium. The resulting shear motion between the otolithic membrane and the macula displaces the hair bundles, which are embedded in the lower, gelatinous membrane.

What is nystagmus?

 * The involuntary rhythmic eye movement consisting of a slow drift in one direction followed by a quick jerk back in the opposite direction. The direction of the beating is named by the quick jerk.  The slow component is in the direction of the ear that is hypoactive, and the quick component is in the direction of the ear that is hyperactive.  That is that a right-beating nystagmus could either mean that the left side is deficient or the right side is hyperactive.

What are the four important things to ask/look for when examining for vertigo?

 * 1) What is the illusion of movement (i.e. spinning, tilting, or falling, etc.)
 * 2) Is there a trigger?
 * 3) How long does it last?
 * 4) Is there nystagmus present? (obviously, the only physical examination component)
 * Also...
 * In regards to the ear, ask about hearing loss, tinnitus, otalgia, otorrhea and facial palsy.
 * In regards to the eyes, ask about diplopia and blurry vision
 * In regards to the CNS, ask about HA, speech disturbance, focal sensorimotor weakness
 * In regards to the heart, ask about orthostatic hypotension and arryjthmia
 * In regards to psych, ask about panic and hyperventilation

What is Benign Paroxysmal Postional Vertigo (BPPV)?

 * In layman’s terms, “your ear rocks are in the wrong place”. Sensations often get worse and then better and can be triggered by looking up.  There may be downward nystagmus as well, but all symptoms go away in <1 minute.  Repetition will fatigue the response.
 * Fast beating nystagmus will go towards the ear with the problem, as this side has a hyperactive vestibular stimulation.
 * It is characterized by sudden vertigo, triggered by head movement in lying back of turning sideways, duration is seconds, and caused by otoliths in the semicircular canal. Diagnosis is by history and Dix-Hallpike test.
 * The Hallpike is done by bringing the patient from sitting to a supine position, with the head turned 45 degrees to one side and extended about 20 degrees backward. Once supine, the eyes are typically observed for about 30 seconds.  If no nystagmus is observed, the patient is brought back to sitting.  There is a delay of about 30 seconds, and then the other side is tested.
 * The prescription is to perform the Epply maneuver. First, go toward the side that is giving discomfort (left or right) and keep the head in that position until the dizziness (vertigo) or rotatory nystagmus goes away.  Then move the head to the opposite side in the same position.  Then have the patient roll to his or her stomach—rolling towards the second side—until the nose is pointed at the floor.  Then the patient sits up and the head is positioned down (neck flexed) approximately 15 degrees so that the horizontal canals are properly horizontal.  This cycle is repeated until symptoms go away in all positions.

What is a dehiscence of the superior semicircular canal?

 * It is a rare disorder.
 * It causes sudden vertigo triggered by loud noise and pressure changes.
 * It is caused by the absence of bone over the superior semicircular canal. Dx by history, audiogram and CT.  Rx is surgery.

What is a vestibular neuronitis/labrynthitis?

 * Both are a very common disorders.
 * There is an initial intense vertigo with a slow resolution. It lasts for hours to days, and is resolved in weeks to months.  It is caused by a viral infection.
 * Vestibular neuronitis may be associated with nausea, vomiting, and previous URI.
 * Labrynthitis is the inflammation of the inner ear. In addition to balance control problems, the patient may encounter hearing loss and tinnitus.  It is usually caused by a virus, but it can also arise from bacterial infection, head injury, extreme stress, and allergy or as a reaction to a particular medication.  However, it often is the sequelae to an URI.

What is a Meniere's Disease?

 * Symptoms are varaible, but generally are episodic vertigo, fluctuating hearing loss, tinnitus and aural fullness. It often presents with one symptom and then generally progresses.
 * There is a lymphatic channel dilation, affecting the drainage of the endolymph. The cause of this is unknown.  It affects people differently from being a mild annoyance to a lifelong disability.
 * Triggers are mostly unpredictable
 * It lasts minutes to hours (i.e. has a medium duration)
 * Rx: Diet (low sodium, cessation of caffeine, EtOH, and smoking) dyazide, IT gentamicin, and surgery if severe enough

What is an acoustic neuroma?

 * Benign tumor of Schwann cells on the vestibular nerve. Also called vestibular schwannoma.
 * Progressive disequilibrium, asymmetric sensorineural hearing loss
 * Acoustic neuromas may occur sporadically, or as part of Von Recklinhausen neurofibromatosis. In neurofibromatosis I, it is typically unilateral.  In neurofibromatosis II, it is bilateral.
 * There is a mass effect danger with these neuromas.
 * Dx: History, audiogram, MRI
 * Rx: Observation, radiation or surgery