Intermittent oculomotor nerve paresis and hollow appearance on MRI manifested by pituitary adenoma

A 71-year-old man had sustained intermittent ptosis and double vision for 2 weeks. Neurological examination found unilateral oculomotor nerve (CN III) paresis manifesting as limitations of gaze, ptosis, and mydriasis. Neither headache nor any other cranial neuropathy was noted. Cerebral magnetic resonance imaging revealed a well-circumscribed mass in the pituitary fossa extending laterally into the left cavernous sinus. The segment of the left CN III lying in the oculomotor cistern was considerably compressed by the tumor. The cisternal segments of the left CN III showed an undescribed, "hollow" appearance. The left orbit and brainstem were intact. The patient underwent tumor resection via an endoscopic transsphenoidal approach. The tumor tissue was soft in consistency, involving xanthochromic fluid. The pathological diagnosis was pituitary adenoma accompanied with considerable hemorrhagic changes. The patent's ptosis and limitations of gaze showed remarkable improvements on postoperative day 1, with resolution of the hollow appearance of the affected CN III that was confirmed on day 3. We assumed that the intralesional bleeds and lateral tumor extension into the oculomotor cistern were associated with the intermittent paresis of the CN III as the sole presentation. A hollow appearance identified in the CN III might indicate a reversible dysfunction of the nerve that can anticipate an improvement by prompt surgical intervention.