Hypotonia, congenital hearing loss, and hypoactive labyrinths

The records of all patients attending a neurosensory genetics clinic over an 11-year period were reviewed. Of the 450 patients seen, 31 presented with sensorineural hearing loss, hypotonia, and delay in the acquisition of motor milestones. Of these, 4 children were found who did not have an etiologic diagnosis such as Down syndrome or cerebral palsy. Vestibular testing revealed hypoactive labyrinthine function in all 4 of the cases, and careful imaging of the temporal bone showed anomalous development of the cochlea, vestibule, and semicircular canals in 3 of the 4 cases. None of the patients had ataxia, tremor, or significant nystagmus. Over time, the hypotonia improved in all, and none were felt to have cognitive deficits. These cases demonstrate that hypoactive labyrinthine function may be associated with hypotonia that is severe enough to result in delayed acquisition of motor milestones. The patients followed the typical remitting course of "benign congenital hypotonia." The distinguishing clinical feature is the presence of moderate to profound sensorineural hearing loss in all of the patients.