[Ipsilateral gustatory disturbance by thalamic hemorrhage]

Area of Science:

• Neuroscience
• Neuroanatomy
• Sensory pathways

Background:

• Animal studies suggest the gustatory pathway ascends ipsilaterally in the brainstem to the thalamus (nucleus ventralis posteromedialis parvocellularis, VPMpc).
• The anatomical arrangement of the human gustatory pathway remains incompletely understood.
• Previous case reports hinted at an ipsilateral brainstem pathway for taste in humans.

Observation:

• A 35-year-old male presented with double vision and a midbrain hematoma.
• The patient subsequently developed right-sided oral cavity sensory disturbance (dysesthesia) and total hypogeusia (reduced taste).
• MR imaging confirmed the hematoma extended to the ipsilateral thalamus.

Findings:

• This case provides the first evidence of unilateral gustatory disturbance resulting from an ipsilateral thalamic lesion.
• The findings support the hypothesis that the human gustatory pathway ascends ipsilaterally through the brainstem and thalamus.
• Unilateral thalamic lesions causing taste impairment may also involve sensory deficits in the ipsilateral oral cavity.

Implications:

• This study contributes to understanding the neuroanatomical basis of human taste perception.
• It highlights the thalamus as a critical relay for ipsilateral gustatory information.
• Further research is warranted to fully elucidate the central taste pathways in humans.