Syndromes of the Pontile Tegmentum

Abstract

The pons is divided dorsoventrally into three portions, the tegmentum lying in the center, with the basis situated ventrally and the tectum dorsally. Each portion has certain syndromes connected with it, although there is not uncommonly some overlapping. Most present knowledge concerning the various structures in the pons has come from clinicopathologic studies, reaching back at least eighty years. Briefly considered, the syndrome of the basis is predominantly motor, since the pyramidal tracts are located ventrally. Unilateral lesions, occurring in response to thrombosis of small branches of the basilar artery, are by no means infrequent in cases of cerebral ateriosclerosis, but are seldom large enough to produce a severe degree of hemiplegia. Sometimes such a lesion can be recognized by the great degree of spasticity without involvement of sensibility or language. Bilateral lesions of the base of the pons are a frequent cause of pseudobulbar palsy.1 Much of the emotional explosiveness seen in patients with multiple sclerosis can be attributed to interruption of the conducting pathways for volitional movements in the basis pontis with preservation of the mechanism for mimetic movements lying more dorsally.2 One of us (W. F.),3 in a series of 100 brains of psychotic persons, in which the pons was sectioned minutely, found 14 specimens with small focal lesions of the pons. Such lesions may well underlie the weakened emotional control observed in persons with cerebral arteriosclerosis even in the absence of demon¬ strable "strokes."Damage to the tectum of the pons results in a major "cerebellar" syndrome because of the interruption of the dentatorubral connections,' but a lesion in this vicinity (possibly involving the tegmentum) will also produce on the opposite side a lack of mimetic response with preservation of voluntary movement, the reverse of spasmodic laughing and crying.2Lesions of the tegmentum of the pons produce a variety of symptoms, depending on the particular location. Since the pons is a rather large structure, small focal lesions may occur in different portions, with production of isolated signs, but more often there are combinations of signs which have been erected into various syn-From the

Benign Cerebellar Tumour Presenting a Modified Foville Syndrome

“…According to Freeman, Ammerman and Stanley (13), in only a few cases has this syndrome been reported to result from an extra-pontine lesion, and in these the lesion was usually massive and in such location as to exercise considerable pressure on the pons. In the present case the lesion also obliterated the fourth ventricle and led to hydrocephalus.…”