Thursday, November 26, 2009

The Larynx for Neurologists

Meyer TK. The Neurologist 2009; 15:313-318. Also points from Rosenfield DB,and Viswanath NS. Evans R. Diagnostic Testing in Neurology Philadelpia, Saunders, 1999, pp. 223-229.

Larynx functions: phonation, deglutition, airway protection, control of respiration. Laryngeal closure also allows increased abdominal pressure for defection, parturition and stabilization of thorax for heavy lifting.Humans have a lower larynx than grazing animals,helping phonation but more precarious for airway control.

Parkinson's disease-- vocal folds are atrophied and bowed with incomplete closure. Patients perceive their own hypophonic speech as of adequate loudness. Voice is also due to bradykinetic efforts from inadequate bellows mechanism (diaphragm and chest wall). Treatment includes bilateral bulking injections to vocal cords to facilitate glottal closure which can be temporary or permanent. Lee Silverman voice technique also helps.

Vocal Cord paralysis. Patient has weak breathy wet voice. It usually occurs due to tumor or surgery. If one vocal cord does not close, can do implant medialization, which will improve voicing and cough in all, and speech in 70 %.

Spasmodic dysphonia-- is a focal dystonia of 2 types. Adductor s.d. is characerized by harsh strangled quality with voice breaks. Abductor s.d is characterized by sustained breathiness with breathy voice breaks. The dystonia is task specific, eg. with breathing, sparing other functions such as swallowing. SD is female predominant with 73 % ADSD, 17% ABSD. Its associated with essential tremor in 30 % and other dystonias in 14 %. Botox is best treatmentfor both types, although the procedure is different for each.

Historical points in dysphonia. Getting stuck,shaking, or improving with alcoholsuggests ET. Trauma can cause dislocated arytenoid cartilage. Pain indicates focal pathology or GERD. Abrupt onset maybe psychogenic. Fluctuations may represent myasthenia.


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