July 23, 2013
A patient came to our office with complaints of uneven hearing, balance difficulty and tinnitus in the poorer hearing ear. This condition did not happen overnight, but had worsened over time. The woman was fearful she would lose hearing in the other ear and not regain her balance functions.
Audiologists are trained in the recognition of “red flags”, or telltale signs of conditions requiring further medical investigation. The patient’s history often speaks volumes about potential diagnoses, therefore, we ask very specific questions regarding risk factors, other medical conditions and new or changing symptoms. Diagnostically, we seek symmetry in the clinical signs from right ear to left. The majority of hearing loss cases affect both ears to a similar degree. A “bad ear” and a “good ear” raise immediate suspicion. Add difficulty with balance, vertigo, atypically poor word recognition, gait disturbance, headache, pressure sensations and one-sided ear ringing, and we begin to suspect the possibility of “retrocochlear disease”, which refers to pathology along the nerve pathway connecting the inner ear to the brain.
A common retrocochlear disorder is an acoustic neuroma. It is often said that “vestibular schwannoma” is a more accurate term, as the tumor arises from Schwann cells instead of neurons themselves, and the vestibular portion of the auditory nerve is more commonly affected. The canal through which the nerve travels through the temporal bone towards the brainstem is the site of lesion. The area known as the “cerebello-pontine angle” is often implicated. This growth is generally benign (non-cancerous) and slow growing. Since the presence of this neoplasm disrupts the synchrony of firing of individual nerve fibers along the nerve, one test that can aid in diagnosis is an ABR (acoustic brainstem response), a type of EEG, although most otolaryngologists prefer an MRI imaging study of the cerebello-pontine region.
Treatment is generally surgical, and is a decision made between otologist and patient. Hearing may be spared, although not necessarily improved, by surgical management. The otologist may choose to observe the tumor and symptoms over time before proceeding with treatment. The patient will often be left with a significant hearing asymmetry. This can generally be habilitated with a hearing aid if residual hearing is sufficient to derive benefit from amplification. Thorough diagnostics, including intensive word recognition testing, will help determine the potential benefit of hearing aids. The first step, as always, is a thorough diagnostic workup and a discussion of all appropriate options.