This is an uncommon condition that typically affects women in their 3rd and 4th decades. It is often associated with a high body mass index (BMI) – overweight individuals. The precise cause is poorly understood, but the underlying problem leads to raised pressure inside the ventricles (fluid filled cavities) of the brain. Since the ventricles communicate with the optic nerve at the back of the eye, pressure can be exerted, causing visual symptoms and visual loss.
Precipitating causes in addition to the characteristics found above include:
- Steroid use
- Pregnancy
- Oral contraceptive use
- Tetracyclines (A class of antibiotic)
Symptoms
- Headache – characteristically worse upon waking
- Audible pulsation in the ears – pulsatile tinnitus
- Transient episodes of visual loss, precipitated by bending over or straining
- Double vision, intermittent or permanent
- Dizziness, nausea and vomiting
Signs (what the Dr can see)
Swelling of the nerve in the back of the eye called papilloedema.
The optic nerve head is swollen and pushing forwards into the back of the eye. The normal cup-shaped
depression (the physiological cup) has been effaced and the blood vessels are dilated – this is called Papilloedema.
Tests
- Vision, including colour, will be tested, as well as visual fields.
- A CT or MRI scan will be performed to exclude more sinister causes. The results are normal in BIH.
- Lumbar puncture – this will test the pressure in the spinal fluid (which is connected to the brain) and will be found to be elevated in BIH
Treatment
Generally this condition is managed in conjunction with a neurologist.
- Observation, weight reduction and ceasing causative drugs may be all that is required for milder cases.
- Diuretic drugs that reduce spinal fluid production are used – Diamox tablets.
- In severe cases, where the sight is damaged or threatened, surgery may be performed, either on the optic nerve or to insert a bypassing shunt.
In general this condition can be very successfully managed to reduce unwanted symptoms and to prevent sight loss. The Diamox tablets may initially cause tingling of the fingers and an intolerance of fizzy drinks. They can usually be tapered down to acceptable levels.
