Isolated bilateral trochlear nerve palsy as the first clinical sign of a metastatic [correction of metastasic] bronchial carcinoma.

Purpose: To report a case with isolated, nontraumatic bilateral fourth nerve palsy as the first clinical sign of a metastatic lung carcinoma.

Methods: Case report. A 56-year-old man presented with isolated, nontraumatic bilateral fourth nerve palsy. Magnetic resonance imaging (MRI) of the brain and orbits and, subsequently, chest x-ray and a computer tomographic (CT)-scan of the thorax, the abdomen, and the pelvis were performed.

Results: Magnetic resonance imaging confirmed the presence of a midline brain stem lesion in the region of decussation of the trochlear nerves. Computed tomographic scan of the chest revealed that the lesion was caused by a metastatic lung carcinoma.

Conclusion: The findings of isolated bilateral fourth nerve palsy in the absence of trauma should alert the clinician to the possibility of a posterior fossa lesion in the region of the trochlear nerves. Besides urgent scanning of the dorsal midbrain, investigations should be directed to search for the primary tumor.