Auditory neuroma originates from the auditory nerve sheath and is a typical nerve sheath tumor. Since the nerve itself is not involved, the proper term should be: auditory nerve sheath tumor. It is one of the most common intracranial tumors. It is most common in middle-aged people, with a peak in the 30s and 50s.
Symptoms and signs
The tumor will push or compress the auditory nerve, vestibular nerve and the accompanying internal auditory artery, which in turn will affect the blood supply to the inner ear, as a degeneration of sensory structures, manifesting as unilateral slowly progressive (occasionally sudden) deafness, high pitched tinnitus, dizziness and a sense of instability. If the middle nerve and facial nerve are pushed, there will be pain in the ear, change in secretion of salivary gland and lacrimal gland, abnormal taste sensation in front of tongue, facial muscle spasm, muscle weakness or paralysis. If the tumor contacts with brainstem and cerebellum and compresses them, it may cause spontaneous nystagmus and ataxia. If the tumor is too large, it may cause obstruction of peripheral venous reflux and cerebrospinal fluid circulation, which may increase intracranial pressure and lead to headache, nausea and vomiting.
Clinical manifestations
(1) Early symptoms.
(1) Tinnitus: it is one-sided, with varying pitch and progressive increase, mostly starts at the same time with hearing loss, but it may be the only symptom in early stage.
② Hearing loss: progressive deafness on one side, early often manifested as hearing the sound without knowing its meaning when talking with others, gradually developing into total deafness.
③Vertigo: A few of them show transient rotational vertigo with pressure in the ear, nausea and vomiting, such as symptoms of fluid accumulation in the membranous vagus, but most of them show a sense of instability; because of the slow development of the tumor, vestibular compensation gradually occurs and the vertigo may disappear.
(4) Pain deep inside the affected ear or mastoid, numbness of the posterior wall of external auditory canal.
(2) Symptoms when the tumor has invaded or originated in the posterior cranial fossa.
(1) Involvement of sensory branch of trigeminal nerve; ipsilateral facial numbness.
(2) Ipsilateral peripheral facial palsy may appear.
③In advanced stage, the tumor compresses the cerebellum, then vocalization is unclear and movement disorders appear.
④Headache: initially located in the occipital and parietal regions, and in advanced stage, full headache due to increased intracranial pressure; it may also be accompanied by visual impairment and involvement of cerebral conduction tract.
Diagnostic tests
1, pure tone audiometry is unilateral tone neural deafness, the curve is mostly high frequency steep descending type, a few are flat type or rising type, self-described audiometric curve is mostly type III, IV, occasionally see type II, tone decay test is overwhelmingly positive, binaural alternating loudness balance and short incremental sensitivity index test without loudness reshock phenomenon, loudness discomfort threshold is elevated, speech recognition rate is significantly decreased, mostly around 30%. Acoustic conductance test: the tympanic chamber conductance map is normal, the stapedius muscle acoustic reflex threshold is elevated or disappeared, the latency is prolonged, and there is often pathological attenuation. Cochlear electrogram tracing: if there is no inner ear blood supply disorder, CM can remain normal, AP wave is significantly widened, and its response threshold is often lower than pure tone hearing threshold. Auditory brainstem evoked potential tracing shows that the V-wave latency and the I-V interval on the affected side are significantly longer than those on the healthy side, and even the V-wave disappears.
2. Vestibular function examination: most patients can use nystagmography to trace spontaneous nystagmus to the healthy side, and the response to various evoked tests is generally low, often with a dominant bias to the affected side.
3, neurological examination, most of the patients showed V, VII, IX, X, XII cerebral nerve involvement, and the protein content of cerebrospinal fluid examination was elevated.
4. Imaging examination: X-ray plain film or tomography film of each projection of the rock cone shows enlargement of the inner ear canal on the affected side, deformation or destruction of the bone wall. Brain pool imaging of the inner ear canal, CT and MRI can not only find very small or tumors that have not entered the inner ear canal, but also show the relationship between the shape of the middle stream and the surrounding tissues.
Diagnosis: The diagnosis is mostly confirmed based on typical symptoms and examination findings. The difficulty lies in early diagnosis and is also valuable in early diagnosis, which needs to be differentiated from sudden deafness and Meniere’s lesion.
Treatment options
Surgical treatment is preferred for auditory neuroma, which can be completely removed and cured. Gamma knife treatment can be considered if the tumor remains from surgery.