SUPERIOR SEMICIRCULAR CANAL DEHISCENCE

This disorder, SCD, is caused by thinning of the layer of bone that normally separates the brain from the inner ear. An abnormal connection develops over time, usually between the upper (superior) balance canal of the inner ear and the brain. It can cause a combination of any of the following symptoms:

• Hearing loss
• Hyperacusis (over-sensitivity to noise)
• Tinnitus – any pitch, pulsatile or hearing ocular movements
• The ear feeling blocked
• Distortion of sound in the ear, particularly being sensitive to one’s own voice (Autophony)
• Becoming dizzy from loud noises
• Becoming dizzy from pressure changes – blowing nose, straining, pushing on or into the ear
• Imbalance
• Headaches/Migraines

It is a fairly common finding on cat scan (CT) studies, present in 3-9% of CTs, but CT can be inaccurate and over-call the condition and not all patients with SCD on CT have symptoms. The incidence of the symptomatic form is 0.5-2%. It is more common in women. It occurs in the left ear in 40%, right ear in 35% and occurs in both ears in 25% of patients. Symptoms can start after a head injury or barotrauma, but usually the onset is gradual without a specific event in most people. There is evidence that it may be congenital in some people as has been seen in CTs of pediatric patients. The age of onset of symptoms is usually in the 40s. Obesity, increased intra-cranial pressure and sleep apnea may play a role.

It can be suspected from taking a history of your symptoms, your exam findings, and your audiogram. It is confirmed with CT scanning and a special test called a vestibular evoked myogenic potential study (VEMP). Other exams of the function of the inner ear may be ordered.

Several treatment options are available. These including observation without intervention if symptoms are mild, a simple plugging of a natural opening in the middle ear with a short procedure entering under the ear drum, or occluding the hole and/or ends of the balance canal and/or placing tissue between the brain and inner ear. These procedures are longer and approached either through the mastoid cavity of the ear or through the skull via a middle fossa craniotomy. The surgical approach depends on the location and size of the hole and the anatomy of the surrounding bone.

If migraine symptoms are also present, or the main complaint is imbalance, a course of balance therapy, a migraine diet and migraine medicine is usually prescribed before considering surgery.