Page 393 - Clinical Anatomy

ECA6 7/18/06 6:54 PM Page 378

378 The central nervous system

,,

Fig. 265◊The central connections of the auditory pathway of VIII.

Clinical features

1◊◊Lesions of the cochlear division result in deafness which may, or may
not, be accompanied by tinnitus.
The differential diagnosis between middle ear deafness and cochlear
(inner ear) or auditory nerve lesions can be made clinically by the use of a
tuning fork. Air conduction (the fork being held beside the ear) is normally
louder than bone conduction (the fork being held against the mastoid
process). If the middle ear is damaged, the reverse will hold true.
2◊◊Apart from injury to the cochlear nerve itself, unilateral lesions of the
auditory pathway do not greatly affect auditory acuity because of the bilat-
erality of the auditory projections.
3◊◊ Temporal lobe tumours may give rise to auditory hallucinations if they
encroach upon the auditory (superior temporal) gyrus.