Making the deaf hear and the dumb speak

Abstract

Alaryngeal speech is now a necessary part of the rehabilitation of patients after laryngectomy. Voice reconstruction is more often successfully accomplished with tracheoesophageal fistula (TOF) valves (figure) than with oesophageal speech (90% vs 33%). T O F speech is also of better quality. The development of indwelling TO F valves further reduces patient dependence on the hospital environment, as the median survival of Provox valves is 45 months (DeCarpentier). To subject patients to the rigours of the development of oesophageal speech product ion knowing that only 33% will even achieve vocal proficiency now seems cruel. Cochlear implantation is now accepted clinical practice for providing auditory stimulation to profoundly deaf adults and children. Cochlear implants transduce sound energy into coded electrical signals which bypass nonfunctioning cochlear hair cells via an electrode array implanted into the scala tympani to stimulate the cochlear nerve. These impulses are conducted to the auditory cortex to restore hearing. Cochlear stimulation may be achieved by either single-channel or mult iple-channel stimulating electrodes. Only multichannel devices can be expected to result in open-set speech discrimination (word recognition without any knowledge of the possible optional response). Following the pioneering work of Wilson, the continuous interleaved sampling (CIS) strategy has been developed commercially. CIS continually codes the entire acoustic signal, closely simulating the normal hearing ear. A 12-channel implant gives 18 144 pulses/s. This strategy produces marked improvement in speech-perception tests. It has now been shown (Ann Otol Rhino Laryngol 1995; 104: 19-24) that mult ichannel devices provide significantly greater benefit than single-channel devices. Overnight pulse oximetry shows that sleep apnoeic Tracheoesophageal fistula valve in situ, showing the principle of alaryngeal speech With permission from International Healthcare Technologies, Carpenteria, CA 93013-2918, USA.