Hereditary motor sensory neuropathy type Lom (synonyms: HMSN 4D, Charcot-Marie-Tooth 4D, CMT4D): A Case Report

Introduction Hereditary motor sensory neuropathies are a very heterogeneous group of neuropathies with now more than 100 known possible affected genes and a prevalence of 1/2500. For the demyelinating subtype Charcot-Marie-Tooth 4D (CMT 4D), progressive demyelination of the cochlear nerve with subsequent deafness has been described. The reason for the affection of the peripheral auditory pathway in this form of CMT is unclear so far. A causal therapy does not exist to date.

Case A now 22 year old patient who had been diagnosed with CMT 4D in 2007, was first presented 5 years ago for audiological assessment. Since diagnosed he was receiving Gabapentin and Amitriptyline. The clinical examination demonstrated normal findings in pure tone and speech audiometry, as well as regular transient evoked otoacoustic emissions (TEOAEs). Average gradients of auditory brainstem response audiometry (ABR) demonstrated prolonged latencies. The patient described new-onset fluctuant symptoms with recurrent hearing loss and tinnitus bilaterally. Regular magnetic resonance imaging (MRI) of the neurocranium showed no central pathology besides dilated cerebrospinal fluid spaces. With progression of the demyelination the results of the pure tone and speech audiometry demonstrated corresponding findings. In our clinic there is a possibility to conduct single sweep analysis in BERA as a new form of diagnostics. These results differed significantly from normal findings.

Conclusion With this new form of analysis for single sweep evaluation in BERA, computer-based parameters to judge a desynchronization can be electrophysiologically recorded and rated. Further research regarding pathophysiology and causal therapy approaches of the disease is necessary to further improve the progression of the disease.

Publication History

Article published online:
12 May 2023