Pathology of Paget's Disease of the Temporal Bone
The Paget disease is a chronic osteodystrophy of unknown etiology, and is characterized by abnormal bony resorption and deposition.
It affects 3% of the population over forty years of age and males more frequently than females.
This anatomo-radiologic syndrome is sometimes accompanied by clinical symptoms.
Paget disease may be monostotic or polyostotic but never generalized.
The disease principally affects the axial skeleton.
The skull and temporal bones become involved in about two-thirds of the patients.
Progressive involvement of the temporal bones may lead to alteration of position, increase in size and change of architecture of the petrous pyramid, external canal, middle ear and inner ear capsule.
These changes in turn may produce impairment of hearing (about 30-50% of cases) and vestibular function (20-25%).
Cases of deafness due to Paget's disease can be separated into two types :
(1) deafness of a mainly mixed type in which progressive aggravation occurs particularly in the inner ear, and
(2) perceptional deafness which progresses without involvement of the transmission apparatus.
Temporal bone involvement in Paget disease can result in hearing loss by a variety of mechanisms. One such mechanism is compression of neural structures within the internal auditory canal.
The histopathology reveals Pagetic bone invading the internal auditory canal and compressing the cochlear division of the VIIIth cranial nerve resulting in severe neural degeneration.
There are no other histopathologic abnormalities present in the cochlea to explain the hearing loss.
Differential Diagnosis: Otosclerosis
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