[Illustration: FIG. 76. TO ILLUSTRATE THE PRESSURE EFFECTS OF A TEMPORO-SPHENOIDAL ABSCESS:--(1) _upward_ pressure on the lower cortical motor area, and (2) _inward_ pressure on the internal capsule. T.S., Temporo-sphenoidal abscess; _a._, Cortical area for lower extremity; _b._, Cortical area for upper extremity; _c._, Cortical area for face; C.N., Caudate nucleus; L.N., Lenticular nucleus; I.C., Internal capsule; O.T., Optic thalamus.]
_Aphasia_ will partake of the motor or sensory type according to the situation of the abscess. Thus, motor aphasia indicates pressure on Broca’s area, sensory points to the involvement of the region of the angular gyrus (see p. 163). According to Schmiegelow, some type of aphasia was present in 23 out of 54 cases of otitic temporo-sphenoidal abscess.
_Facial paralysis_, whether due to inward or upward pressure, is of the incomplete or cortical type, the upper face-muscles escaping or being but slightly affected. No difficulty need be experienced in differentiating between the ipso-lateral paralysis which results from destruction of the facial nerve in the aqueductus Fallopii and the contra-lateral palsy dependent on the cortical lesion.
Pressure may also be exercised on the post-Rolandic sensory areas and on the tracts that evolve therefrom, but the general condition of the patient seldom allows of any accurate diagnosis with respect to sensory involvement in general.
When the abscess is of considerable size, both _third_ and _sixth_ nerves may be involved. For instance, the third nerve, emerging from the brain at the anterior border of the pons, and passing along the inner border of the temporo-sphenoidal lobe, is liable to irritation or pressure paralysis. In the former case, the pupil on the affected side will be contracted, in the latter instance dilated. When _ipso-lateral_ third nerve paralysis coexists with paralysis of the opposite face and upper extremity, a condition of crossed paralysis results.
When the sixth nerve is involved the external rectus on the side of the lesion is paralyzed with resultant internal squint. Conjugate deviation of the eyes towards the side opposite to the lesion and secondary lateral nystagmus have both been observed.