Spinal N13 versus cortical N20 and dermatomal somatosensory evoked potential studies in patients with cervical radiculopathy

Most studies on somatosensory evoked potentials [SEPs] in cases of cervical radiculopathy routinely analyze scalp [cortical] responses [mixed or dermatomal SEPs], depending mainly on evaluation of N20 whose origin is the primary somatosensory cortex. It was suggested that selective study of the N13 potential, might be a useful technique to improve both accuracy and sensitivity of the diagnosis of cervical radiculopathy. The aim of our study was to test the sensitivity of the spinal N13 potential in uncovering lesions of cervical nerve root; and to compare it to dermatomal and mixed nerve SEPs. Forty patients with clinical suspicion of cervical nerve root lesion had been selected. Twenty normal subjects constituted the control group. Magnetic resonance imaging [MRI] of the cervical spine was performed for all patients to reveal the presence of any cervical nerve root compression. The following electrophysiological studies were done [sensory and motor conduction studies of the median and ulnar nerves, mixed SEP of median nerve, dermatomal SEP and spinal N13 SEP study of the median nerve. There was a positive correlation between the mixed and the dermatomal SEPs and between the mixed SEP and N13. On the other hand there was a positive correlation between the dermatomal SEPs and N13. There was a positive correlation between the MRI and the mixed SEP, the dermatomal SEP and N13, respectively. Sensitivity and specificity of N13, dermatomal somatosensory evoked potentials [DSEP] and mixed SEP were determined using MRI as a gold standard. N13 is the most sensitive followed by DSEP and the least was the mixed somatosensory evoked potentials [MSEP]. They were all specific with a high positive predictive value. N13 had the highest negative predictive value followed by DSEP and the least was MSEP and we concluded from this study that N13 is a sensitive technique which is suitable for detecting early and mild symptomatic cervical nerve root lesion

Assessment of risk factors responsible for difficult weaning from mechanical ventilation in adults

The aim of this work is to identify the most important risk factors responsible for difficult weaning from mechanical ventilation in adult patients. A prospective cohort study. Respiratory Intensive care unit of Alexandria main University Hospitals. Thirty one patients requiring mechanical ventilation with difficult weaning according to Brochard's classification. After failure of weaning on PSV mode of mechanical ventilation, the patient is reevaluated to detect the risk factors responsible for difficult weaning. Eighteen patients [58%] were successfully weaned and thirteen [42%] failed weaning trials and finally died. Of the thirty-one studied cases, 16 [52%] were males. Mean age of the studied patients was 57.7 +/- 15 and mean BMI was 30 +/- 7.9. Twenty-one patients [67.7%] required prolonged mechanical ventilation and ten [32%] required less than 14 days. Mean of Rapid Shallow Breathing Index measured during SBT was 56 +/- 9 breaths/min per L among cases who were successfully weaned from MV and 122 +/- 19 breaths/min per L among those who failed weaning trials. Mean CROP index value was 38.7 +/- 11 ml/breath per min among cases who were successfully weaned and of significantly lower value 7.5 +/- 2.6 ml/breath per min among those who failed weaning trials and finally died, [p = 0.00]. In the present work; risk factors that found to be responsible for failure of weaning trials were recent infections [pulmonary and/or extra-pulmonary] that were detected in all the studied cases [100%], disturbances in the trace elements and electrolytes in 26 cases [83.8%], cardiovascular dysfunctions in 18 [58%], psychological problems in 12 [38.7%], endocrinal disturbances in the form of hypothyroidism in 3 [9.6%], nutritional deficiency in 27 [87%], neuromuscular dysfunctions in 14 [45%] and other additional co-morbid problems as hepatic or renal impairment in 15 patients [48%]. In the present work; EMG and nerve conduction study was done to 19 cases with difficult weaning. The results showed 26% with normal picture, 63% with moderate to severe axonal sensory motor peripheral neuropathy and 10.5% with a picture of myopathy. Regarding the effect of neuromuscular dysfunctions on the outcome of MV, in the present study, 33% of the patients with polyneuropathy failed weaning trials and finally died [p = 0.798]. The present study stresses on the importance of neuromuscular assessment in all cases with difficult weaning as this may be an important contributing factor for difficult weaning and prolonged mechanical ventilation. All potential causes of ventilator dependency should be identified when a patient is difficult-to-wean. Then, a plan should be developed that uses a multidisciplinary team approach to correct the reversible causes of weaning failure and facilitates weaning thereafter

Subclinical central nuropathy in thype 2 diabetes mellitus

Involvement of the peripheral and autonomic nervous systems is frequently encountered in diabetes mellitus [DM]. However, there is a paucity of data regarding central neuropathy in DM. To evaluate central nervous system neuropathic changes in patients with type 2 DM with and without peripheral neuropathy. The study included three groups; group 1: Fifteen patients with type 2 DM with clinical and electrophysiological findings of peripheral neuropathy, group 2: Fifteen patients with type 2 DM without any clinical or electrophysiological evidence of peripheral neuropathy and group 3: Fifteen healthy subjects as a control group. All groups were age and sex matched and subjected to physical examination, laboratory investigations including: Complete blood cell count, fasting plasma glucose. glycated hemoglobin [HbAlc], serum lipid profile, renal fitnctions and other necessary tests, in addition to the electrophysiological study including: Somatosensory evoked potentials [SEP], motor evoked potentials [MEP], visual evoked potentials [VEP] and brainstein auditory evoked potentials [BAEP]. Group I had a statistically significant higher mean values of fasting plasma glucose, HbAlc, urinary albumin excretion [UAE] and serum creatinine compared with group 2. Both diabetic groups had similar changes in VEP P100 latency and its amplitude, MEF central motor conduction time, amplitude percentage quotient and duration of the MEP, and BAEP wave II latency, with statistically significant differences compared to healthy controls. There was a statistically significant delay in all of the BAEP waves interpeak latency only in group 1. The other tested parameters of central neuropathy showed statisticasly signficant differences between all studied groups. A statistically significant positive correlation was observed between some of the studied parameters of central neuropathy in diabetic patients and each of the patient age, duration of diabetes, HbA1c, serum total cholesterol, serum triglycerides and UAE. Central neuropathy in type 2 diabetics is not uncommon even in absence of peripheral neuropathy. It is related to the patient age, duration of diabetes, glycated hemoglobin value, dyslipidemia and diabetic nephropathy. The use of more than one modality of the electrophysiological tests [multimodal evoked potential studies] can buffer the fallacies of a single mode and is advisable in evaluating central neuropathy in patients with type 2 DM. Early diagnosis of central neuropathy is recommended to offer an early opportunity for a proper management

Motor evoked potentials in motor neuron disease: parameters of evaluation and its relation to disease severity

Transcranial magnetic stimulation [TMS] is a technique that can activate cortical motor areas and the corticospinal tract without causing discomfort to the patients. To evaluate the parameters of motor evoked potentials [MEP] induced by TMS in motor neuron disease [MND] and their relations to the severity of the disease. Twenty five subjects with motor neuron disease [MND] who had been diagnosed as MND using the standard clinical and electrophysiological studies [nerve conduction studies, 5MG and the somatosensory evoked potential studies] had been subjected to TMS and the MEP parameters [threshold, central motor conduction time [CMCT,], amplitude percentage quotient, phases and duration of the MEPs] were determined. Ten matched healthy persons were selected as control. Functional evaluation and disease severity assessment had been scored using the amyotrophic lateral sclerosis [ALS] Functional Rating Scale [ALSFRS] and the ALS Severity Score [ALSSS] respectively and compared to the control group. There was a statistical significant difference of all the studied parameters between patients and the control group. The mean central conduction time [CMCT] was correlated with the severity of the disease, while the amplitude changes were evident in late stages especially when associated with bulbar manifestations whereas there was no correlation between MEP parameters and the functional rating scale. From these findings it would be recommended to use the TMS to predict the severity of MND