Jacewicz - Dizziness Flashcards
Is dizziness a “common” complaint?
- Sure
- Nearly 20% of elderly pts experience dizziness every year that restricts their activity, and often prompts a doctor’s visit
What are some of the things a pt can “mean” when they say they are experiencing dizziness?
- Presyncope: feeling faint, lightheadedness
- Loss of balance, unsteadiness of gait
- Vertigo: spinning, swaying, illusion of mvmt
- Other: double vision, psychological dissociative feelings, vague sensations (hypoglycemia, drug intoxication, giddiness)
What are some things that can elicit orthostatic hypotension?
- Lower body venous pooling, i.e., squatting
- Intravascular volume depletion: bleeding, prolonged vomiting, severe diarrhea, polyuria, dehydration
- Medication effect: beta blocker can dampen heart’s response (INC CO) to change in BP and DEC cerebral perfusion
- Autonomic neuropathy: can be produced by DM, amyloidosis, Guillan Barre -> peripheral vasoconstriction mediated by SYM NS fails to respond to orthostatic falls in BP
- Vasovagal rxn: viewing first autopsy
What are some cardiac causes of syncope and near-syncope?
- Cardiac arrhythmia
- CHF
- Obstructed cardiac outflow: aortic valvular stenosis, cardiac tamponade, idiopathic hypertrophic subaortic stenosis
- Pulmonary embolism
What are some things that can lead to gait imbalance in the elderly?
- Etiology is often multifactorial, but neuronal loss due to aging or disease can occur in:
1. Cerebellar function: stroke, aneurysm
2. Vestibular function: prior head trauma
3. Visual orientation: cataracts
4. Peripheral nerve function: position sense in legs - NOTE: redundancy in neuronal circuits lost
How can longstanding HTN in the elderly lead to gait ataxia?
- Small vessel disease affectts the white matter of the brain, and for unclear reasons, the frontal areas are affected the most
- This disconnects frontal lobes responsible for planning gait from basal ganglia that permit smooth coordination of gait
- Patients can develop apraxia of gait -> devo difficulty knowing how to walk
What is one thing that can improve gait in the elderly regardless of etiology?
- Physical therapy
- Can often improve gait no matter what the multiple reasons are for falling gait, known or unknown
- Always worth a trial
How is psychiatric dissociation related to gait?
- Pt who feels distant from the real world and has home stressors may complain of “dizziness” that is hard to pin down or define
- May have past or current depression, panic attacks, anxiety neurosis, or psychosomatic personality
- Can do neuropsych MMPI test to help detect tendency toward somatization
- Consult psych
What is “true” vertigo? What is its clinical sign? How is it lateralized?
- Illusion of movement (whirling, spinning, swaying) due to a disease of the vestibular system
- Often accompanied by N/V
- CLINICAL SIGN = nystagmus
1. Defined by the fast component (saccade)
2. Brain suppresses visual blur (too fast for retina to process) during saccade, so vision only possible during slow phase of eye mvmt -> room spinning to R = slow phase to L
What are some of the etiologies for a complaint of “I am dizzy?” This is a big flow chart, so break it down.
Briefly describe the concept of 6 degrees of freedom.
- Linear motion along x, y, and z axes (translational motion)
- Angular rotations about each of these (rotational motion):
1. x = roll
2. y = pitch
3. z = yaw
Which organs in the vestibular system are responsible for sensing linear motion and the effects of gravity?
- SACCULUS (aka, saccular macula): coplanar with the vertical axis
- UTRICLE (aka, utricular macula): coplanar with the horizontal axis
- They detect static head positions (degree of tilt) and linear accelerations within their plane
Which organs in the vestibular system detect rotational motion?
- AMPULLA in each of the 3 semicircular canals detect rotational acceleration or deceleration within the plane of the canal, aka angular movements
- CUPULA inside ampulla transduces this info for each semicircular canal
What are these, and why are they integral in head mvmt? Describe them, and the cellular structure of the utricle and saccule.
- OTOLITHS (otoconia): tiny crystals of Ca carbonate on top of gelatinous membrane -> stuck to membrane and sufficiently heavy to distort matrix by linear force during mvmt and by gravitational forces at all times
- Sensory hair cells w/stereocilia are embedded in this gelatinous matrix
- During change in head position, plane of utricle and saccule changes its orientation to gravity, producing a change in shear stress on the membrane
1. Direction and degree to which cilia become deformed results in proportional INC or DEC of electrical impulses along vestibular N
How does the distortion of a hair cell produce a signal?
- STEREOCILIA project into ENDOLYMPH rich in K+, and force toward KINOCILIUM opens K+ channels in the cilia -> K+ influx depolarizes the cell membrane
- Depolarization activates voltage-gated Ca channels, causing INC in IC Ca concentration (Ca conc inside cell is 104x lower than outside; very little Ca needed to cause marked INC in IC Ca)
- Ca activates Ca-dependent K+ channels that extrude K+ into K+-poor PERILYMPH bathing sides/base of hair cell
- Counterbalance activities allow electrical resonance of membrane to shift up or down in freq and modulate conc of Ca at hair cell base -> rise in local Ca conc triggers release of GLUTAMATE or ASPARTATE (NT)
What is the next step in the transduction of sound after opening of Ca channels? What happens if force is applied to hair cells in the opposite direction?
-
