Anatomical structures in the Leksell pallidotomy target

Objective: Because interruption of pallidal outflow signals by pallidotomy is believed to play an important role in the motor improvement in Parkinson's disease, the anatomical relationship of the two major pallidofugal tracts, namely the ansa lenticularis (AL) and the fasciculus lenticularis (FL) to the Leksell pallidotomy target (LPT) were studied. Methods: Magnetic resonance (MR) scans of 20 patients with Parkinson's disease were studied. The scans were obtained in the inversion recovery and fast spin echo sequences and viewed in the reverse video mode. Results: The pallidofugal tracts appeared as bands of high intensity on MR scan. FL was wide and extended from the posterior half of the globus pallidus interna (GPi) medially into the internal capsule. AL was narrow, parallel and posterior to the anterior commissure, parallel to and 3 mm above the optic tract, and just beneath the FL. The part of the FL immediately lateral to the internal capsule overlapped the lateral end of the AL. The center of this overlapping area was termed the 'overlapping point' (OP). In all cases, the OP was within the range of LPT. Conclusion: It is concluded that the structures in the LPT are FL and AL; and therefore, this procedure could also be known as 'fasciculoansatomy'.