Specificity of "peering at the tip of the nose" for a diagnosis of thalamic hemorrhage.

BACKGROUND Tonic inward and downward deviation of the eyes ("peering at the tip of the nose") is regarded as a unique feature of thalamic hemorrhage, but the mechanisms of this ocular finding remain obscure. OBJECTIVES To describe 4 patients who showed tonic inward and downward deviation of the eyes from brainstem or thalamic lesions and to discuss the possible mechanisms involved. DESIGN Case report. SETTING Secondary and tertiary referral hospitals. RESULTS One patient developed alternating esotropia with downward ocular deviation from thalamic hemorrhage compressing the midbrain. Two patients showed multiple infarctions in the territory of the posterior circulation with or without the involvement of the thalamus. Another patient had lateral pontine hemorrhage extending up to the midbrain tegmentum. Ocular bobbing preceded or accompanied tonic ocular deviation in 3 patients. CONCLUSIONS Tonic inward and downward deviation of the eyes may develop in thalamic or brainstem lesions. Irritation or destruction of the neural structures involved in the vergence and vertical gaze may cause this ocular sign in mesodiencephalic lesions. Skew deviation and esotropia from abduction deficit may be involved in some patients. Ocular bobbing and tonic downward deviation may share a common pathogenesis.