Flashcards in PBL - Schwannoma Of Vetsibulocochlear Nerve Deck (62)
Define the term tinnitus.
Perception of sounds in the absense of external auditory stimulus
What three things cause tinnitus.
Sounds produced by adjacent structures
Other disease processes
What sounds can be produced by tinnitus
Ringing of the ears
Which two ways can tinnitus be defined?
What is objective tinnitus?
Sound is potentially detectable by another observer
What are the causes of objective tinnitus?
Vascular abnormalities or neuromuscular disorders
- sounds generated by turbulent blood flow conducted into auditory system
What is subjective tinnitus
Noise perception when there is no noise stimulation in the cochlear
What can cause transient tinnitus in normal people?
Name some conditions associated with more persistent subjective tinnitus.
Noise induced hearing loss
Prebycusis - sensorineural hearing loss
Cochlear of labyrinthine infection
What is the suggested pathophysiology of tinnitus?
Abnormal firing of auditory receptors
Dysfunction of cochlear neurotransmitters function or ionic balance
Alterations in central processing of the signal
Illusion of motion associated with disorders of vestibular function
Define objective and subjective vertigo?
Objective - person is in motion and environment is stationary
Subjective - person is stationary and environment is in motion
What are some differential diagnoses of vertigo?
What can unstable gait be caused by?
Disorders of sensory input
Vertigo can be caused by peripheral and central vestibular problems, what is the difference between them?
Peripheral - severe in intensity, and episodic
Central - mild and consistent
Describe motion sickness.
Normal physiological vertigo caused by repeated rhythmical stimulation of vestibular system
Symptoms of motion sickness
- lowered BP
Hyperventilation - can causes pooling of blood in lower extremities
What is the pathology of Ménière's disease?
Occurs due to distension of the endolymph compartment of the inner ear
What is the 'triad' of Ménière's disease?
What are the suggested mechanisms that may cause Ménière's disease.
Increased endolymph production
Decreased production of perilymph accompanied by compensatory increase in endolymph sac
Decreased endolymph absorption
- caused by malfunction of endolymph sac or blockage of endolymphatic pathways
Name five things which are thought to cause Ménière's disease.
Infection - syphilis
Endocrine - adrenal-pituitary insufficiency and hypothyroidism
What is Ménière's disease characterised by?
Fluctuating episodes of tinnitus, feeling of ear fullness, violent rotatory vertigo
What happens to hearing loss as Ménière's progresses?
Stops fluctuating and progressively worsens
Both ears become affected
What happens to the vertigo as the Ménière's progresses?
Episodes of vertigo diminish and disappear although the person may be unsteady
List the differential diagnoses of Ménière's disease
- acoustic neuroma
- otitis media
- too toxic drugs
- vertebrobasilar insufficiency
- autoimmune disease
What is a schwanomma of the vestibulocochlear nerve?
Benign Schwann cell tumour affecting CN VIII
How does a schwanomma cause unilateral sensorineural hearing loss?
Compresses the cochlear nerve of interferes with the blood supply to the nerve and cochlear
What genetic problem is through to cause tumour growth?
Tumour suppressor gene abnormality on chromosome p22 (schwanomma protein)
How do patients with a schwannoma present?
Episodes of vertigo