Ear, Nose & Throat
A 45 year old man presents to the Emergency Department with a chronic history of unilateral hearing loss, facial numbness and tinnitus. You suspect an acoustic neuroma. Which of the following conditions is a risk factor for development of an acoustic neuroma?
Answer:
A coexisting diagnosis of neurofibromatosis type 2 increases the prevalence of acoustic neuroma. This rare autosomal dominant disorder causes benign tumours on the vestibulocochlear nerves and other locations.Acoustic Neuroma
Ear, Nose & Throat
Last Updated: 8th September 2021
Acoustic neuroma (vestibular schwannoma) is a benign cerebellopontine angle tumour that grows from the superior vestibular component of the vestibulocochlear nerve, usually presenting with unilateral sensorineural hearing loss. Larger tumours can cause significant problems with cerebellar problems, increased intracranial pressure, and obstructive hydrocephalus, and, as a result, may be life threatening.
Risk factors
A coexisting diagnosis of neurofibromatosis type 2 increases the prevalence of acoustic neuroma. This rare autosomal dominant disorder causes benign tumours on the vestibulocochlear nerves and other locations.
Clinical features
Patients may have minimal symptoms, as tumours grow slowly. Signs and symptoms may not always correlate with tumour size.
- Common symptoms
- Unilateral sensorineural loss
- Intermittent dizziness (caused by cerebellar compression or vestibular dysfunction)
- Unilateral facial numbness (caused by compression of trigeminal nerve)
- Tinnitus
- Less common symptoms
- Headache
- Unilateral facial weakness
- Altered tear production on affected side
- Metallic or reduced taste on affected side
- Diplopia on lateral gaze
- Nystagmus
- Swallowing difficulties
- Loss of balance and coordination difficulties
- Slower blink
- Gait disturbance
- Features of hydrocephalus or raised intracranial pressure
Investigations
Patients with unilateral hearing loss (especially if progressive) not responding to local ear care warrant referral for audiology testing, auditory brainstem reflexes and ENT consultation.
All patients with sensorineural or retrocochlear findings on audiometry, especially if asymmetrical, are recommended for a gadolinium-enhanced MRI or computed tomography (CT) of the head (depending on what is available). The gold standard investigation is a gadolinium-enhanced MRI scan as it is more sensitive than CT scanning. Positive findings on MRI include a cerebellopontine angle lesion extending into the internal acoustic meatus. Absence of the dural tail is considered conclusive. MRI determines the size and location of the tumour, which allows the patient and clinician to formulate a treatment plan. Additionally, MRI is used to monitor growth of a tumour if resection is deemed unsuitable.
Management
Patient management is influenced by local experience in focused radiation and surgical approach. Specific recommendations to patients, tumour size limits, and age and hearing level limits will vary greatly depending on local experience. The rates of facial nerve, hearing, and quality of life preservation for the different treatments also vary due to local experience.
Management includes observation as well as treatment. Smaller tumours in patients with minimal symptoms (e.g. mild hearing loss) may be followed up with serial scanning, especially if there is no documented growth. Treatment choices include focused radiation (stereotactic radiotherapy and stereotactic radiosurgery) and surgery. Chemotherapy is ineffective.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
