Motor nervous pathway function is impaired after treatment of childhood acute lymphoblastic leukemia: A study with motor evoked potentials

Background. The objective was to evaluate whether motor nervous pathways ar e affected when patients are treated for childhood acute lymphoblastic leuk emia (ALL). Procedure, thirty-two children with ALL were studied at the end of treatment by means of motor evoked potentials (MEPs) elicited by magnet ic stimulation (MS) transcranially and peripherally and underwent a detaile d neurological examination. Thirty-two healthy children matched with them f or age. sex, and height served as a control group. Results. The latencies o f the MEPs were significantly prolonged along the entire motor nervous path way in the patients with ALL compared with the healthy controls, indicating demyelination in the thick motor fibres. The MEP amplitudes of the distal extremities elicited by stimulation at the brachial plexus and LV spinal le vel were significantly lowered in the patients treated for ALL, also indica ting anatomical or functional loss of descending motor fibres and/or muscle fibres. The MEP amplitudes elicited by cortical MS showed wider variation and no clear abnormalities were found. Neurological signs and symptoms were common after treatment: 41% of the patients had depressed deep tendon refl exes, 31% had fine motor difficulties and 63% gross motor difficulties, and 34% had dysdiadochokinesia. The conduction delay within the peripheral ner ve was related to the post-therapeutic interval after administration of vin cristine and the lesions within the CNS to the number of injections of intr athecal methotrexate. Conclusions. The present results show adverse effects of the ALL treatment on the entire motor nervous pathways. In our experien ce, the measurement of MEPs by MS provides an objective. painless, and prac tical tool for assessing the treatment-related neurotoxicity in both the CN S and the peripheral nerves. These disturbances in the motor nervous pathwa ys at the end of treatment raise the question of the long-term effects of A LL treatment on the motor nerve tracts, and have led us to employ MEP5 to s tudy these effects in long-term survivors of ALL. Med. Pediatr. Oncol. 36:3 45-351, 2001. (C) 2001 Wiley-Liss, Inc.