A English gentleman who heard his eyes scratching “like sandpaper” every time they moved in their sockets has been cured. The man was suffering from a rare condition called superior canal dehiscence syndrome (SCDS) and affects only one in 500,000 in the United Kingdom after being discovered a decade ago.

Symptoms are caused by a thinning or complete absence of the part of the temporal bone overlying the superior semicircular canal of the vestibular system. This may result from slow erosion of the bone or physical trauma to the skull and there is evidence that the defect or susceptibility is congenital.

A dull ache in the man’s head progressed to a vibrating sensation that affected his vision every time he spoke. Meanwhile loud noises started to make him feel dizzy.

Richard Irving at the Birmingham Ear Clinic, who diagnosed him with the rare condition after noticing part of the bone covering the semicircular canals is missing, which exposes the sensitive membrane underneath. It is not hard to treat, but very hard to identify.

There are normally only two points of increased compliance (yielding to pressure) in the inner ear: the oval window, through which sound energy is transmitted into the inner ear via the stapes bone; and the round window, through which sound energy is dissipated from the inner ear after traveling around the cochlea. SCDS creates a third mobile window into the inner ear. Signs and symptoms of SCDS result from the physiological consequences of this third window.

Vestibular and/or auditory signs and symptoms can occur in SCDS. Vertigo and oscillopsia (the apparent motion of objects that are known to be stationary) evoked by loud noises and/or by maneuvers that change middle-ear or intracranial pressure (such as coughing, sneezing, or straining). Persons with SCDS may experience a feeling of constant disequilibrium and imbalance, and may perceive that objects are moving in time with their pulse (pulsatile oscillopsia). Auditory manifestations of SCDS may include autophony (increased resonance of one’s own voice), hypersensitivity to bone-conducted sounds, and an apparent conductive hearing loss revealed on audiometry.

Once diagnosed, the gap in the temporal bone can be repaired by surgical resurfacing of the affected bone or plugging of the superior semicircular canal. These techniques are performed by accessing the site of the dehiscence either via a middle fossa craniotomy or via a canal drilled through the transmastoid bone behind the affected ear.

Irving said:

“It is very unusual with symptoms which could easily have been dismissed. It must have been very distressing.”

According to current research, in approximately 2.5% of the general population the bones of the head develop to only 60-70% of their normal thickness in the months following birth. This genetic predisposition may explain why the section of temporal bone separating the superior semicircular canal from the cranial cavity, normally 0.8 mm thick, shows a thickness of only 0.5 mm, making it more fragile and susceptible to damage through physical head trauma or from slow erosion.

An explanation for this erosion of the bone has not yet been found.

Written by Sy Kraft