Injury to the third nerve can occur during surgical procedures near the cavernous sinus, and repair may be attempted using either primary end-to-end anastomosis or interposition nerve grafting. However, in some situations, preservation of the proximal portion of the nerve may not be possible. Treatment options are restricted to frontalis muscle sling for ptosis and eye muscle surgery for strabismus. We report long-term outcome of surgical anastomosis of the intracranial segment of the fourth nerve to the distal stump of the third nerve at its entry into the cavernous sinus during surgical removal of a third nerve schwannoma.
A 34-year-old woman presented with 4 months of progressive right arm, face, and leg weakness along with slurred speech. Her right eye was amblyopic. Visual acuity was 20/200, right eye and 20/25, left eye. Neurologic testing revealed mild right upper motor facial weakness and moderate spastic right hemiparesis with increased tone and reflexes. Computed tomography (CT) and magnetic resonance imaging (MRI) of the brain demonstrated a 4.5-cm lobulated cystic mass occupying the suprasellar, interpeduncular, and prepontine cisterns with compression of the thalamus, midbrain, and pons (Fig. 1). Left temporal craniotomy was performed with subtemporal and presigmoid transtentorial exposure of the middle and posterior cranial fossae. The superior petrosal sinus was divided and the tentorium was split from lateral to medial. The tumor was totally removed and was found to be schwannoma of the third nerve (1–9).
The third nerve arose from the anterior aspect of the tumor, and its fibers were splayed over the anterior capsule. Attempts to preserve the nerve were unsuccessful. Primary repair or interposition grafting also were not possible. Accordingly, the remnant of distal third nerve at the cavernous sinus was trimmed leaving a healthy 5-mm stump. The fourth nerve was divided at its entry into the tentorium and anastomosed to the third nerve stump. A small platform was fashioned by placing a piece of gelfoam under the third nerve on the posterolateral cavernous sinus wall and sealing it with fibrin glue. The fourth nerve was placed snugly against the stump of third nerve on the platform and the anastomosis created with fibrin glue (Fig. 2).
Postoperatively, a complete left third nerve palsy was present with a fixed dilated pupil. During follow-up, the patient learned to initiate certain movements to reposition her eyes and lift her ptotic left eyelid. In primary gaze, the right eye was open and centered, the left eye closed. On downward gaze, the right eye looked down with partial lid closure, whereas the left eye was open and centered (Fig. 3; see Video 1, Supplemental Digital Content, http://links.lww.com/WNO/A54). She was able to partially open the left eye with both eyes centered (see Video 2, Supplemental Digital Content, http://links.lww.com/WNO/A55) and to adduct the left eye well past midline (see Video 1, Supplemental Digital Content, http://links.lww.com/WNO/A56). She was unable to execute saccades or make vertical eye movements with the left eye. At 8 months after surgery, the patient regained slight adduction with partial left lid elevation. By one year, there was full eyelid opening with the left eye adducted to midline. Six years after surgery, the patient uses her amblyopic right eye for navigation, and her 20/25 left eye for reading and watching television. If she looks downward the left eye predictably opens and, occasionally, the left eye opens involuntarily.
During surgery, for tumors involving the third nerve, preservation of the nerve usually is only possible with partial tumor removal or when the tumor is very small. If the nerve has been surgically divided, and the cut ends are close to each other, primary nerve anastomosis may be performed. If the 2 nerve ends are further apart, there is the option of interposition grafting (Table 1) (1–9). If neither technique is possible, the eyelid and eye muscle surgery may be offered to the patient.
We used a novel approach, dividing the fourth nerve and anastomosing it to the distal stump of the transected third nerve. We believe that the fourth nerve would be of limited value without a functioning third nerve. Tonic and perhaps voluntary innervation from the fourth nerve might provide control of the levator and medial rectus muscle. Frisen et al. (10) first attempted a left fourth to third nerve anastomosis in an 18-month-old boy with bilateral third nerve palsies. There was improvement in ptosis and adduction of the left eye, but the effect lasted only 8 months.
In our patient, levator function was restored although not to the degree seen in Frisen’s case. Rather than a tonically open eye, our patient learned to control the levator by looking downward. With restored adduction, the eye opened in a centered position. The patient learned to shift her visual attention to the affected (left) eye during television viewing or reading fine print, while using her amblyopic (right) eye for general viewing and activities requiring saccadic eye movements.
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