Clinical and electromyographic deep tendon reflexes in polyneuropathy: diagnostic value and prevalence*.

BACKGROUND: Evidence is accumulating that patients with polyneuropathy may present with normal clinical deep tendon reflexes (C-DTR). There are few studies that assessed the diagnostic utility of electromyographically recorded DTR (Er-DTR) in patients with polyneuropathy. OBJECTIVES: The objectives of this study were twofold: (i) to evaluate the prevalence of preserved C-DTR in polyneuropathy; (ii) diagnostic value of Er-DTR latency measurement in patients with polyneuropathy. METHODS: We prospectively studied 38 controls and 185 patients with polyneuropathy. All subjects had evaluation of C-DTR, Er-DTR obtained from right biceps brachii (BR), right patellar (PR) and bilateral ankle reflexes (AR). RESULTS: Of these 185 patients, 118 (63.8%) had chronic axonal neuropathy (CAN), 49 (26.5%) demyelinating polyradiculoneuropathy (DPN) and 18 (9.7%) small fiber neuropathy (SFN). The C-DTR were normal in 65 patients whereas 39 of these 65 (60%) patients had abnormalities of Er-DTR at one or more sites. Er-DTR latencies in patients with polyneuropathies were prolonged at all sites compared with controls (P < 0.01). Among patients with various types of polyneuropathies the Er-DTR, mean latencies at all the sites and latency indicative of demyelination (>150% of the normal mean) were higher in patients with DPN than that of CAN or SFN (P < 0.01). CONCLUSIONS: We conclude that C-DTR are preserved in 35.1% of the patients with polyneuropathies and Er-DTR should be performed in such patients in order to provide electrophysiological evidence of a polyneuropathy. Er-DTR are useful in distinguishing axonal from demyelinating disorders of peripheral nerve, and detection of subclinical involvement of large fibers in SFN.

Early diagnosis of carpal tunnel syndrome: comparison of digit 1 with wrist and distoproximal ratio.

Our objective in this study was to compare the sensitivity and specificity of the median sensory nerve conduction velocity (SNCV) from digit 1 to wrist with those of the distoproximal (D/P) ratio of the median SNCV from palm to digit 3/palm to wrist in the diagnosis of mild carpal tunnel syndrome (CTS) by using a receiver operating characteristic (ROC) curve. To achieve this objective, we studied prospectively (January 1997-October 1998) 370 patients referred for CTS. One hundred forty-two patients (38.4%) with moderate to severe CTS and 15 patients (4.1%) with multiple (> or = 3) compressive neuropathies in upper limbs with subclinical peripheral neuropathy were excluded. The remaining 213 patients (302 hands with mild CTS; 167 women; mean age, 50 y +/- 12 y) and 38 controls (71 hands; 25 women; mean age, 47 y +/- 13 y) had median and ulnar nerve conduction studies. ROC curves were constructed for median SNCV digit 1 to wrist and median SNCV D/P ratio from the patients' and controls' data. The median SNCV at < or = 45.9 m/s, corresponding to an optimal cutoff point on ROC curve, discriminated 89.5% of mild CTS from controls with specificity of 98.6%. The median D/P ratio at > or = 1.12, corresponding to an optimal cutoff point on ROC curve, discriminated 67.2% of mild CTS from controls with specificity of 97.2%. Of the 10.3% (31/302) of hands in which digit 1 to wrist was within normal limits at the selected optimal cutoff value (< or = 45.9 ms), 7% (21/302) had an abnormal D/P ratio (> or = 1.12), and 3.3% (10/302) had a normal electrophysiologic examination. The likelihood ratio (true-positive ratio to false-positive ratio, assessing the discriminative power of a test) of the median SNCV digit 1 to wrist, at an optimal point on ROC curve (63.9), was higher than that of the median SNCV D/P ratio (23.9, chi2 = 36.9, P < .001). These findings suggest that the median SNCV digit 1 to wrist is more sensitive than the median SNCV D/P ratio in the diagnosis of mild CTS.

Sympathetic skin response and heart rate variability in patients with Huntington disease.

OBJECTIVE: To examine the autonomic nervous system functions in patients with Huntington disease. BACKGROUND: Although patients with Huntington disease frequently experience vegetative symptoms, it is not clear if there is dysfunction of the autonomic nervous system. METHODS: Sympathetic skin response (SSR) latency and amplitude from both palms and soles and R-R (heart rate) interval variation (RRIV) at rest and during the Valsalva maneuver were examined in 22 patients and 21 age-matched controls. Unified Huntington's Disease Rating Scale scores were determined in all the patients. RESULTS: Our data are reported as means +/- SEMs. The SSR latencies in patients (mean palm latency, 1835.8+/-110.7 milliseconds; mean sole latency, 2625.3+/-226.9 milliseconds) were prolonged compared with controls (mean palm latency, 1359.5+/-28 milliseconds [P<.01]); mean sole latency, 2038.1+/-44.9 milliseconds [P<.01]) and amplitudes in patients (mean amplitude, 1063.1+/-237.7 microV) were smaller compared with controls (mean amplitude, 1846.3+/-251.2 microV [P<.05]). The RRIV in patients both at rest (mean RRIV in patients, 3.7%+/-0.4% vs. controls, 9.7%+/-0.6% [P<.01]) and during the Valsalva maneuver (mean RRIV in patients, 6.3%+/-1.6% vs. controls, 14.5%+/-1.2% [P<.01]) was lower compared with controls. Furthermore, the prolonged SSR latencies, smaller amplitudes, and lower RRIV in patients compared with controls closely correlated with the various components of the Unified Huntington's Disease Rating Scale scores (total behavior score and SSR latency, R = 0.6 [P<.01]; total behavior score and SSR amplitude, R = -0.5 [P<.05]; total behavior score and RRIV, R = -0.4 [P<.05]; verbal fluency and SSR latency, R = -0.5 [P<.05]; verbal fluency and SSR amplitude, R = 0.5 [P<.05], verbal fluency and RRIV, R = 0.5 [P<.05]; total functional capacity and SSR latency, R = -0.6 [P<.01]; total functional capacity and SSR amplitude, R = 0.5 [P<.05]). CONCLUSION: These results suggest that there is autonomic nervous system dysfunction in patients with Huntington disease.

Evidence that alterations in presynaptic inhibition contribute to segmental hypo- and hyperexcitability after spinal cord injury in man.

We examined Hoffmann (H) and tendon (T) reflexes in 3 populations of adult subjects: acute SCI (< 2 weeks post injury), controls, and chronic SCI (> 1 year post injury). We further investigated the effects of continuous tendon vibration and different stimulus rates on the size of evoked H reflexes in these subject populations. All reflex amplitudes were expressed as a function of the maximum direct muscle response (M wave), to allow comparison between subjects. Both H and T reflexes were successfully elicited from all subjects examined, including those in 'spinal shock.' Tendon vibration caused a marked attenuation of H reflexes in acute SCI subjects, intermediate attenuation in controls, and relatively little effect in the chronic SCI group. H reflexes showed greatest attenuation for a given stimulus rate in acute SCI subjects compared to controls (intermediate attenuation) or chronic SCI (limited attenuation) subjects. Both rate sensitivity and vibration influence have been linked to presynaptic inhibitory mechanisms. We suggest that spinal cord injury disrupts the supraspinal influence over segmental interneurons mediating presynaptic inhibition, and that the hyporeflexia associated with 'spinal shock' is due in part to a substantial increase in the efficacy of presynaptic inhibition. Conversely, over time the level of presynaptic inhibition of ankle extensor Ia input in SCI subjects declines to levels less than those of control subjects, contributing to the enhancement of spinal reflexes consistent with the clinical state of 'spasticity' seen in chronic SCI.

Human T lymphotropic virus type I-associated myelopathy. A report of 10 patients born in the United States.

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy (HAM) (tropical spastic paraparesis/HAM) has rarely been reported in the United States. We present 10 well-documented cases with positive Western immunoblot test results and polymerase chain reactions for HTLV-I. The clinical and laboratory features of these American-born patients resemble those previously reported series of tropical spastic paraparesis and HAM from the Caribbean and Japan, but important differences were observed. In our study there were equal numbers of whites and blacks and of men and women. Age at onset was younger than that reported from the Caribbean and Japan. Rate of progression to paraparesis varied but was more rapid than previously reported. Half were transfusion recipients but six had multiple sexual partners, with one regularly interacting with prostitutes and reporting a history of drug abuse. Although more rapid progression was seen in the transfusion recipients, this did not explain the earlier age of onset in this group of patients. The HTLV-I, and the associated myelopathy, are endemic in Florida, suggesting that immigration from, and proximity, to the Caribbean basin are contributing risk factors.

Myokymic discharges: prompt cessation following nerve root decompression during spine surgery.

In surgical cases during which spine nerve roots are at risk, we have found it useful to monitor EMG from the muscles supplied by those roots. Mechanical irritation of a root results in muscle activity, whose amplified signals can be broadcast over a loudspeaker, providing immediate feedback to the surgeon that the root is being irritated. We report here on a patient undergoing spinal canal decompression and fusion following a burst fracture of the L5 vertebral body sustained five days previously. EMG was continuously monitored from the tibialis anterior (TA) and medial gastrocnemius (MG) muscle groups bilaterally. During the period leading up to decompression, myokymic discharges from the left TA muscle were observed, whereas the other 3 muscles monitored did not show such activity. These semi-rhythmic and repetitive discharges from the left TA ceased immediately following surgical removal of a bone fragment compressing the left L5 nerve root. This indicates that the site of axonal irritation was the nerve root, and that myokymic discharges secondary to acute axonal compression can cease immediately upon nerve root decompression.

Sensorimotor myeloradiculoneuropathy in thymoma.

This is the first report describing the clinical, electrophysiological, and neuropathological findings in a patient with thymoma and sensorimotor myeloradiculoneuropathy. Degeneration of the Clarke's nucleus and posterior horns were noted in addition to segmental demyelination and variable axonal loss of the anterior and posterior roots. The segmental demyelination was more severe in the anterior roots of the lower thoracic and lumbosacral regions. A possible rare association between paraneoplastic myeloradiculoneuropathy and thymoma is suggested.

The prevalence and extent of vibration sensitivity impairment in men with chronic ethanol abuse.

We have studied vibration sensitivity impairment in 100 male alcoholic veterans and 52 control subjects who had no etiologic factors for peripheral neuropathy. Vibration sensitivity was quantitated at the hallux with the Vibration Sensitivity Tester. Alcoholic subjects had impairment of vibration sensitivity when compared with control subjects (p less than .001). This difference persisted when a covariance analysis was performed which included age (coefficient +/- SE: 1.40 +/- 0.35 units, p less than .001). Asymptomatic subjects also had vibration sensitivity impairment (p less than .01). In subjects whose ages were greater than or equal to 45 years, 47% of the alcoholics had poorer vibration sensitivity than did any of the controls. Among the alcoholic subjects there were significant correlations of the vibration perception threshold with both age (r = 0.39, p less than .001) and drinking duration (r = 0.35, p less than .001). In multiple regression analyses these associations remained significant (p less than .05). These data indicate that vibration sensitivity impairment is highly prevalent in alcoholic subjects and that impairment may even occur in those who are asymptomatic.

Motor units in incomplete spinal cord injury: electrical activity, contractile properties and the effects of biofeedback.

The electrical and contractile properties of hand muscles in a selected population of quadriplegic subjects were studied intensively before and after EMG biofeedback. Spontaneously active motor units and units that could only be slowly and weakly activated were observed in these subjects, in addition to units that were voluntarily activated normally. This suggests a considerable overlap of surviving motor neurons to a single muscle that are below, near or above the level of a lesion. Despite the common occurrence of polyphasic potentials and other signs of neuromuscular reinnervation, the average twitch tension of single motor units in hand muscles of quadriplegic subjects was not significantly different from that in control subjects. Nor did it increase after biofeedback training that typically increased the peak surface EMG by a factor of 2-5 times. The percentage of spontaneously active units was also constant. The surface EMG may be increased during biofeedback by using higher firing rates in motor units that can already be activated, rather than by recruiting previously unavailable motor units.

Rehabilitation therapy for patients with long-term spinal cord injuries.

The functional effects of three types of therapy for subjects with long-term incomplete cervical spinal cord injuries were investigated. Men and women, aged 18 to 45 years, were assigned to one of four groups using a restricted randomization process. The training period was divided into two consecutive eight-week time blocks where subjects received either (1) supervised physical exercise therapy (PET), (2) neuromuscular stimulation (NMS), or (3) electromyographic (EMG) biofeedback. Group 1 received EMG biofeedback followed by PET; Group 2 received EMG biofeedback followed by NMS; Group 3 received NMS followed by PET; and Group 4 received 16 weeks of PET. Dependent measures (manual muscle tests, self-care scores, mobility measures, and voluntary EMG activity) were assessed before training, at eight weeks, and after 16 weeks of training. A significant improvement (p less than .05) across time was found on all dependent measures except voluntary EMG. No difference was found on comparisons between groups.

Determinants of quantitative sensory testing in non-neuropathic individuals.

We have studied characteristics of subjects that could potentially influence quantitative sensory measurements in 156 non-neuropathic individuals. All subjects had measurements of vibration perception at the hallux and index finger with the vibration sensitivity tester and measurements of cool and warm perception at the hallux with the thermal sensitivity tester. Age, height, and skin temperature were all inversely related (P less than 0.05) to vibration sensitivity at the hallux, while age was inversely related (P less than 0.01) to vibration sensitivity at the index finger. In multiple regression analyses the significant associations persisted (P less than 0.01). Neither cigarette smoking nor the occasional use of alcohol were related to the quantitative sensory indices. These data indicate that age, height, and skin temperature should be considered in the assessment of vibration perception and that thermal sensitivity is relatively resistant to these factors.

Specific assessments of warm and cool sensitivities in adult diabetic patients.

We have specifically examined warm and cool sensitivities in 60 diabetic and 43 nondiabetic individuals. Diabetic patients tended to have less warm and cool sensitivity than the control subjects (P less than .001 for age less than 50 yr and P less than .05 for age greater than or equal to 50 yr). Both patients asymptomatic for neuropathy and patients with symptoms had impairment of warm and cool sensitivity (P less than .05 for comparisons with control subjects). These differences persisted (P less than .05) in covariance analyses with age included as a covariate. There was a nonlinear association between warm sensitivity and hemoglobin A1c. Warm-sensitivity values in the lowest and middle tertiles of the hemoglobin A1c distribution were similar; however, warm-sensitivity values of patients in the highest tertile were markedly increased (P less than .05 for the comparison of the highest tertile with the lowest and middle tertiles combined). There tended to be more warm insensitivity than cool insensitivity among the diabetic patients, and this difference increased with worsening glycemia. These data indicate that both warm and cool sensations are markedly impaired in asymptomatic adult diabetic patients. They also suggest that warm sensitivity is more impaired than cool sensitivity, and that this is the result of a stronger association between warm sensitivity and metabolic factors.

Somatosensory evoked potential measurements in percutaneous fluid aspiration from intraspinal cystic lesions.

Two patients were evaluated with somatosensory evoked potentials (SSEPs) before and after CT-guided fluid aspiration from cystic intraspinal lesions. Our objective was to use the information and the clinical response to this procedure to determine the suitability of the patients for surgical intervention. In both patients, one with a pseudomeningocele and the other with a subarachnoid cyst, improvement in their symptoms corresponded to significant changes in their SSEPs. We believe this technique may be useful in selected cases when it is unclear whether cystic intraspinal fluid collections are responsible for the patient's symptoms. An increase in amplitude and/or decrease in latency of SSEPs, along with clinical improvement after fluid aspiration, may indicate the potential benefit of surgical intervention.

Neurofunctional testing for the detection of diabetic peripheral neuropathy.

We have studied associations of neurofunctional testing with other indexes of diabetic peripheral neuropathy in patients unselected for neuropathy. The tests included vibratory sensitivity (assessed with the Vibration Sensitivity Tester and the Biothesiometer) and thermal sensitivity (assessed with the Thermal Sensitivity Tester). Values for diabetic patients were markedly higher than those of control subjects. The neurofunctional tests were strongly correlated with each other. There were also significant associations between the neurofunctional and nerve conduction indexes. Asymptomatic patients had higher values than those of the control subjects for each test. When clinical and nerve-conduction criteria were a better indicator than thermal sensitivity. Neurofunctional testing appears to be useful for both the clinical and research assessments of diabetic peripheral neuropathy.

Influence of height on quantitative sensory, nerve-conduction, and clinical indices of diabetic peripheral neuropathy.

We have examined associations between height and quantitative sensory, nerve-conduction, and clinical indices of diabetic peripheral neuropathy in adult diabetic patients. Vibratory sensitivity was strongly related to height when measurements were made with either the vibration sensitivity tester (P = .02) or the biothesiometer (P less than .01); however, there was no relation between thermal sensitivity (as measured with the thermal sensitivity tester) and height. The peroneal and posterior tibial motor nerve-conduction velocities were inversely related to height (P less than .05 for both). When age and diabetes duration were included as variables in multiple regression analyses, the associations with height became stronger. Clinical indices of peripheral neuropathy were also related to height in these analyses. Glycosylated hemoglobin was significantly related to thermal sensitivity and the peroneal and posterior tibial motor nerve-conduction velocities but not to vibratory sensitivity. These data indicate that height has a marked influence on quantitative sensory, nerve-conduction, and clinical indices of diabetic peripheral neuropathy.