Electron microscopy of the gasserian ganglion in trigeminal neuralgia.

T HE pathogenesis of trigeminal neuralgia has remained an enigma. Its characteristic feature, excruciating, paroxysmal facial pain, may be produced by any number of conditions affecting the Gasserian ganglion either directly or indirectly. These include dental diseases, 64,m inflammation of the sclera, 77 arterial compression of the trigeminal root, 133 bone changes, 11~ cranial and intracranial tumors, 58,67,74 and lesions in the veins of the neck 119 or in branches of the brachial plexus. 180 The causes of "secondary" trigeminal neuralgia have included cerebellopontine angle tumors, 24,58,67 lesions in the tear ducts, 1~ thrombosis of the posterior-inferior cerebellar artery,137 diseases of the mandibular joint,2a,22,150 syringomyelia, 48 chronic otitis media, 166 tuberculous toxemia, 18,a9 nephritis with azotemia, 41 indoxyluria, 85 influenzap I polyneuritis, infectious polyneuritis, n encephalomyelitis, 66 serum sickness, 167 and lead poisoning? 9 In fact there is no part of the trigeminal pathway, f rom the shin to the cortex, where a lesion has not been described? G9 The general belief has been that there are no pathological changes in the trigeminal ganglion itself. Some of this legend, at least, is based upon a single ganglion removed by Victor Horsely and examined by Henry Head, who finally donated the ganglion to anatomy to be used for normal histology instruction? 69 Although other investigators have found a variety of pathological changes in the trigeminal ganglion,65,113,14~ their findings have never been widely accepted, due in part to the fact that even by light microscopy the normal histology of the ganglion has never been clearly defined.l~0,165 Electron microscopy has made the problem even more complicated, for degenerative changes due to aging 165 or to occult ganglionic disease 13~ must be differentiated from tissue artifacts due to manipulation and to fixation. The necessity