=Pupillary changes= are variable. According to Jonathan Hutchinson, the pupil on the affected side becomes dilated, the blood extending inwards towards the cavernous sinus and exercising direct compression of the third nerve. The frequency with which a dilated pupil occurs in cases of middle meningeal hæmorrhage, and the causation thereof, are, however, matters of dispute. Phelps writes as follows: ‘Reference to cases cited show that the so-called Hutchinson pupil may be observed as well in hæmorrhages occurring in other situations than the middle fossa, and in some cases of cerebral lesion without injury at all. There is no reason to doubt that it is the result of cerebral contusion, but in what relation they stand to specific cerebral injuries is undetermined.’
Walton states that ‘doubtless various factors play an important part in producing the dilated pupil, but if disorders of any simple mechanism are to be credited with the production of the Hutchinson pupil or other pupillary changes, the only lesion worthy of the place is disturbance, irritative or paralytic, of the intracranial fibres of the cilio-spinal tract’.
The late Professor von Bergmann, from 70 cases, reports as follows:--
In 39 cases both pupils were markedly dilated (56 per cent.).
In 7 cases both pupils were markedly contracted (10 per cent.).
In 20 cases the pupil on the same side was dilated (30 per cent.).
In 4 cases the pupil on the opposite side was dilated (6 per cent.).
Parsons, in answering some queries in 1903, writes:--
‘I should anticipate from cortical irritation bilateral pupillary dilatation, perhaps more marked on the opposite side: from pressure the opposite effects, so far as mere cortical paralysis goes, but this would be more liable to be vitiated by vascular changes--the complex condition seen in coma. It is very difficult to elicit pupillary constriction by cortical stimuli--very easy to elicit dilatation, but always bilateral though often more marked on the opposite side.’
In cases examined by me the following conditions were found:--
Pupils equal 46 per cent. of cases Pupils constricted on the affected side 36 per cent. of cases Pupils dilated on the affected side 18 per cent. of cases