Dorsal midbrain syndrome, which is characterized by upgaze paralysis, light-near dissociated pupils, eyelid retraction, and convergence retraction nystagmus, can be caused by compression, ischemia, inflammation, or injury to the dorsal midbrain. Although brain metastases are common in certain cancers, including melanoma, only 3 to 5% occur in the brain stem. We present a case of metastatic melanoma from an unknown primary that initially presented as dorsal midbrain syndrome.
After a prodrome of intermittent nonspecific visual symptoms, a 60-year-old male veteran presented with bilateral upgaze paralysis and convergence retraction nystagmus. A single hemorrhagic lesion in the midbrain was causative. An inguinal mass with associated lymphadenopathy was subsequently discovered, and the biopsy from this site revealed malignant melanoma. A primary lesion was never found. The patient underwent surgical resection of the groin lesion and stereotactic radiosurgery for the midbrain metastasis but passed away 6 months after his initial presentation.
The presentation of bilateral vertical gaze paralysis, especially in the company of convergence retraction nystagmus, light-near dissociated pupils, or eyelid retraction, should raise concern for midbrain pathology. Although metastases to the midbrain are rare, they carry a grave prognosis, especially if melanoma is the primary malignancy, and most treatment options are considered palliative.