Sclerosteosis involving the temporal bone: clinical and radiologic aspects

Sclerosteosis is one of the rare, potentially lethal, autosomal recessive, progressive, craniotubular sclerosing bone dysplasias. Syndactyly of the second and third or other fingers is evident at birth. Hyperostosis and sclerosis are most prominent in the skull and tubular bones, and are frequently associated with excessive height and weight. The typical facial deformity is apparent by the age of 5 years. The changes involving the temporal bone include a marked increase in overall dimensions, extreme sclerosis, and narrowing and constriction of the external ear canal, middle ear cleft, internal acoustic meatus, and falloppian canal. Impairment of hearing, as a rule bilateral, is a frequent presenting symptom which may manifest in early childhood. Initially it is an expression of interference with sound conduction; later it may become associated with a loss of sound perception. Impairment of facial nerve function is another salient feature which occasionally is present at birth. As a rule, it manifests initially as a unilateral, recurrent paresis, eventually progressing to a bilateral permanent partial loss of facial nerve function. Since impairments of hearing and facial nerve function are two of the salient features, present at birth or in early childhood, the responsibility for recognizing the disease often falls upon the otolaryngologist. The clinical and radiologic features permit not only early recognition of the disorder but also differentiation from similar bony dysplasias. Hyperosteosis and sclerosis of the skull lead to thickening and distortion of the calvaria, cranial base, and foramen magnum resulting in reduction of the intracranial volume, interference with the cerebral blood flow, resorption of cerebrospinal fluid, and gradual increase of intracranial pressure. Severe headaches resulting from this mechanism often develop in early adulthood, and several patients have died suddenly from impaction of the medulla oblongata in the foramen magnum. Decompression of the transverse sigmoid sinus and jugular bulb may be lifesaving, combined with a posterior, and if necessary, an anterior, craniectomy for decompression. Early decompression of the internal acoustic meatus and falloppian canal may help in the preservation of cochlear and facial nerve function.