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Título

Isolated Third Cranial Nerve Palsy with Pupil Sparing in Pituitary Apoplexy - Case Report

RESUMO

CASE PRESENTATION: We present the case of 54-year-old man with a 5-day-history of sudden onset, severe, pulsatile headache that was worse in the left retroocular region and associated with nausea and vomiting. Two days after the onset, he developed binocular diplopia and left eyelid ptosis. Physical examination showed complete isolated left third cranial nerve (3CN) palsy but the pupil was spared. Head MRI showed a 2.1x1.4x2.1cm pituitary adenoma, without significant cavernous sinus compression. He also had normal TSH with low free-T4 level; low prolactin and testosterone levels; and normal ACTH and cortisol levels. Cerebrospinal fluid had 13 white blood cells/mm3 and 116mg/dL protein. Based on the clinical history and complementary exams we made a diagnosis of pituitary apoplexy (PA). He was transferred to neurosurgery. DISCUSSION: PA is a rare medical emergency caused by abrupt hemorrhaging and/or infarction of the pituitary gland, generally due to a pituitary adenoma. Sudden and severe headache is the main symptom and can be associated with ocular palsy in 52% of the cases. The third 3CN is often the first and the most affected cranial nerve, and is impaired in 50% of the cases, but isolated 3CN palsy is a rare manifestation. Complete nerve palsy characterized by ptosis, impaired pupillary constriction and ophthalmoparesis is the most common clinical presentation, but pupil sparing may occur in 11% of cases of isolated 3NC palsy. Although complete 3CN palsy with pupil sparing is typical of ischemic lesions, compressive lesions may spare the pupil when the pressure of the lesion is evenly distributed and allows the relatively pressure-resistant, smaller-caliber pupillomotor fibers to escape injury; alternatively, the lesion may compress only the inferior portion of the nerve, sparing the dorsal pupillomotor fibers. In addition, several mechanisms have been proposed to explain the occurrence of 3CN palsy in PA, such as direct invasion of the cavernous sinus; compression without invasion, since the nerve is located horizontally in the same plane as the pituitary gland in the lateral wall of the cavernous sinus; and compression of the vasa nervorum of the nerve due to increased pressure. In our opinion, the last mechanism may also explain the sparing of superficial pupillomotor fibers. COMMENTS: PA should be considered an important differential diagnosis in patients presenting with headache and 3CN palsy, even if isolated and with pupil sparing.

Palavras Chave

Third Cranial Nerve; Pupil; Pituitary Apoplexy