The Surgery of the Skull and Brain

by Louis Bathe Rawling

Laceration of the under aspect of the lobe may, by direct involvement of the olfactory region, interfere with the faculties of smell and taste.

Localizing to those parts that minister to the function of speech.

The condition of the patient usually prevents one from obtaining early information as to the power of speech. Isolated lesions of the posterior part of the third left frontal convolution result in motor aphasia, a condition characterized by the inability on the part of the patient to speak, in spite of the fact that comprehension is unimpaired. The brain-injury is, however, seldom so defined as to be characterized by loss of speech without other phenomena. In very close relation to the area responsible for speech is the writing centre, situated at the posterior end of the middle frontal gyrus, near the centre for the movements of the hands and fingers. Injury to this centre results in agraphia and alexia.

Word-deafness

results from lesions implicating the upper temporo-sphenoidal lobe, and word-blindness from injuries to the supramarginal and angular gyri (see [Fig. 57]).

Fig. 57. The Areas concerned in Speech Expression.

Phelps pointed out that the lesion must be an extensive one if the symptoms included under the term sensory aphasia (word-blindness, word-deafness) are to be evolved. No localized injury to any small area suffices, and the cortex must be deeply involved. Lacerations of the brain are usually of so gross a nature that further differentiation is seldom to be obtained. Here it might be noted that the cortical centres responsible for speech and its accessories, word-seeing, word-writing, and possibly word-hearing, are all situated on the left side in normal right-handed individuals. The corresponding areas on the right side may be regarded as ‘silent’ areas, and may be utilized, if desired, for decompression purposes. No operation, with that purpose in view, should be carried out, however, unless the surgeon is assured that the patient is right-handed in his actions. A case has recently come to my knowledge where a right-parietal decompression operation was carried out with disastrous results.

Localizing to the temporo-sphenoidal lobe.

The relation of sensory aphasia to lesions of the temporo-sphenoidal lobe has already been mentioned. The anterior poles of this portion of the brain, a region frequently involved in head injuries, may lead to the development of impaired smell and taste, especially if the lesion includes the uncinate lobe and be situated on the left side. In other respects, the temporo-sphenoidal lobe may be regarded as a ‘silent’ area of the brain.