Pre-existing Peripheral Neuropathy Research Articles

Fasciculations due to verapamil in a patient with neuropathy

A patient with pre-existing peripheral neuropathy developed generalized fasciculations under verapamil which ceased after discontinuation of the drug. It is suggested that the increase in acetylcholine (ACh) release at the neuromuscular junction by verapamil may trigger fasciculation in the state of regeneration at ACh-sensitive sites of axon terminals and immature axon sprouts.

Problems in the use of anticancer drugs in the elderly.

The elderly represent a special challenge to the physician in providing effective cancer chemotherapy. Though they represent the majority of the patients who eventually will need such therapy, until recently little information was available on its use in this population. There are variable age changes in pharmacokinetics, particularly in renal elimination of drug and metabolites, which may necessitate dosage amendment. Concomitant renal impairment or hepatic disease may further alter drug disposition. Other common pre-existing conditions in the elderly also may increase susceptibility to adverse drug effects. For example, the risk of toxicity from doxorubicin and vincristine can be increased in the presence of pre-existing cardiac disease or peripheral neuropathy, respectively. Because of the variability of the ageing process and the effects of concomitant disease, each patient must be assessed on an individual basis. Furthermore, in treatment planning, not only age and health status but also the patient's attitude and the tumour type are important considerations. Chemotherapy for most malignancies appears beneficial and well tolerated in the elderly, and there is little evidence that age per se is a determinant of chemotherapy regimen selection and dosing. The exceptions may be the curable haematological malignancies for which chemotherapy seems less efficacious and more toxic in geriatric than younger patients. The complications of chemotherapy such as vomiting, mucositis and bone marrow depression must be anticipated, diagnosed early and managed aggressively in aged patients. Guidelines are provided to help manage these problems. Chemotherapy in the elderly is still at a relatively early stage of development. Further research is required to establish optimal regimens for use in this population, in particular for curable haematological neoplasms.

Epidural-evoked potentials: A more specific indicator of spinal cord ischemia

The purpose of this experimental study was to examine the differences between peripheral nerve stimulation and direct spinal stimulation in generating cortical somatosensory-evoked potential (SEP) responses for monitoring spinal cord ischemia during thoracic aorta cross-clamping. Adult mongrel dogs ( n = 6) were placed under general anesthesia and a left thoracotomy was performed. A conventional stimulating electrode was placed over the posterior tibial nerve (PN-SEP), and a special bipolar electrode was placed epidurally over the spinal cord at L1-2 (SC-SEP). The aorta was cross-clamped proximal to the left subclavian artery. Stimulations were alternately performed through both electrodes, and SEP responses were continuously monitored. The cross-clamp was released after one hour and the animal was observed for another hour prior to sacrifice. Excellent SEPs were obtained with six stimuli over 3 sec via the SC-SEP stimulus in contrast to the 200 stimulations over 90 sec required for the PN-SEP stimulus. Aortic cross-clamping resulted in a significantly longer mean time to loss of SEPs for SC-SEP (mean ± SEM, 13.7 ± 1.0 min for SC-SEP vs 11.3 ± 0.7 min for PN-SEP, P < 0.05). Likewise, unclamping of the aorta consistently resulted in a shorter mean time to return of SEPs for SC-SEP compared with PN-SEP. These data indicate that direct epidural stimulation for evoked cortical responses is a more sensitive means of determining the adequacy of posterior spinal cord blood flow as reflected by posterior spinal cord function. Thus, direct stimulation of the spinal cord to produce cortical-evoked potentials may enable the surgeon to differentiate more easily between distal hypotension or factors associated with a preexisting peripheral neuropathy and the inadvertent exclusion of critical intercostals during SEP monitoring for intraoperative spinal cord ischemia.