Clinical applications of transcranial bone conduction attenuation in children

It is a common belief that there is no significant transcranial attenuation across the skull by bone conduction (BC). In 32 children with proven unilateral sensorineural hearing loss the unmasked bone thresholds were measured on each side. There was a significant attenuation of BC at 4 kHz. Transcranial attenuation of BC at 4 kHz may explain the difference in sound perception between the two ears when bone conduction amplification is used. Further research should be undertaken to identify the better cochlea in mixed hearing losses.     

Radio frequency hearing: electrostrictive detection and bone conduction

A hearing aid patented by C. R. Schafer and supposedly based on detection of an amplitude-modulated carrier wave in the auditory cortex was re-examined. It is shown here that the hearing aid actually works by bone conduction of sound. It is concluded that detection of the modulation signal occurs by electrical nonlinearities and electrostriction in the bones of the face and skull.     

Audiometric and ophthalmological findings in rubella deafness

In an attempt to study the relevance of ophthalmological changes to the diagnosis of cochlear hearing impairment due to fetal rubella infection, a survey of the literature combined with a clinical investigation was carried out. Based on the investigation of 57 patients, 31% had congenital hearing impairment due to fetal rubella infection. Of these patients, 61% had typical rubella retinal changes. In the remaining 69%, ophthalmoscopy revealed no abnormality, except in 1 patient. As the cause of the hearing impairment in this patient was unknown, it was concluded that the mother had suffered from subclinical rubella infection in the first trimester of her pregnancy. It is concluded that rubella retinitis is found with such a high incidence in rubella children that it can be used as a tool in the diagnosis of cochlear hearing impairment due to fetal rubella infection. Patients with congenital hearing impairment ought to undergo a routine ophthalmoscopy which will detect eventual pigmentary changes.     

Improved peripheral nerve conduction, EEG and verbal IQ after bone marrow transplantation for adult metachromatic leukodystrophy

A 28-year-old woman with a 4 year history of slowly progressing 'frontal dementia' was diagnosed as having adult metachromatic leukodystrophy and was followed for 4 years after bone marrow transplantation (BMT). MRI, neurophysiological tests (EEG, ENeG, VEP, SEP and BAEP) and neuropsychological assessment were performed before, and repeatedly after BMT. MRI showed symmetrical white matter lesions in the frontal and parieto-occipital lobes and in the corpus callosum. EEG showed frontal and temporal slow wave abnormalities and nerve conduction was slow. Neuropsychological tests showed cognitive impairment in executive functions, decline in visuospatial-constructive and spatial memory tasks and disorganized thinking. IQ was low (52), with slightly better values for verbal IQ than for performance IQ. After BMT, the patient was followed for 4 years. Clear improvements were seen in EEG, in peripheral nerve conduction and in neuropsychological tests (especially in verbal IQ). MRI findings were unchanged. We believe that the improvement in our patient resulted from the bone marrow transplantation.     

Abnormal sensory nerve conduction in multifocal demyelinating neuropathy with persistent conduction block

Two patients exhibited chronic, slightly asymmetric weakness and wasting with fasciculations of the upper limb and hand muscles. Motor nerve conduction studies showed features of multifocal conduction block in nerve segments other than those usually involved in entrapment syndromes. The F wave was markedly delayed in the median and ulnar nerves. Transcranial cortical and cervical root magnetic stimulation showed bilaterally delayed thenar responses with normal central conduction time. Needle electromyography demonstrated a chronic denervation pattern with large polyphasic motor units in several muscles of the upper limbs. Sensory symptoms were mild and limited to paresthesias in the fingertips. Sensory nerve conduction velocity and sensory nerve action potential amplitudes were normal in elbow-to-wrist and wrist-to-finger segments of the median and ulnar nerves, but there was a delayed cortical response and unrecognizable Erb's point and cervical responses in the somatosensory evoked potentials to median nerve electrical stimulation. Electrophysiologic examination was normal in most nerves of the lower limbs. These two patients, meeting clinical and electrophysiologic criteria of multifocal neuropathy with conduction block, demonstrate that sensory fibers may also be involved in this syndrome.     

Chloroquine cardiomyopathy with conduction disorders

A 58 year old woman on long term treatment with chloroquine for systemic lupus erythematosus presented with cardiac conduction disorders and heart failure with hypertrophic cardiomyopathy, which was confirmed by histology to be related to chloroquine toxicity. The heart failure improved on stopping chloroquine treatment.     

Alternation of retrograde conduction times

A patient with idionodal rhythm with alternation of retrograde conduction times is described. The idionodal escape rhythm is associated with alternating slow and relatively fast retrograde conduction times to the atria. The mechanisms underlying this phenomenon are discussed.     

Lower extremity sensory nerve conduction studies

The need for routine recording of sensory potentials in the lower extremity was developed in efforts to better investigate peripheral neuropathy. Sensory nerve conduction studies (NCS) are more sensitive to many abnormalities in the peripheral nervous system than the motor NCS responses. This article provides a thorough review of sensory nerve conduction studies of the lower extremity, with special emphasis on electrodiagnostic issues.