Posteroventral pallidotomy for midbrain tremor after a pontine hemorrhage - Case report

This 49-year-old man gradually developed a disabling action tremor in the p roximal right upper extremity 8 months after suffering a pontine tegmental hemorrhage. The intraoperative microrecording in the nucleus ventralis inte rmedius (VIM) of the left thalamus revealed tremor-synchronous grouped disc harges with a vigorous (2.7 Hz) action tremor predominantly in the shoulder and upper arm. High frequency electrical stimulation in the VIM did not af fect the tremor. A posteroventral pallidotomy (PVP) was performed and resul ted in the successful alleviation of all tremor activity. Posteroventral pa llidotomy is known to alleviate parkinsonian tremors, especially those occu rring in the contralateral lower extremity, trunk, and proximal segment of the contralateral upper extremity. The authors consider the pal lidoreticul ar pathway to be an important tremor-mediating pathway for the proximal seg ment of the upper extremities and believe it can be controlled more effecti vely by PVP than by VIM thalamolomy, as demonstrated by the PVP-induced res olution of the midbrain tremor observed in this case.