The utility of F wave chronodispersion in lumbosacral radiculopathy

The sensitivity of F wave chronodispersion (Fc) in evaluating nerve root pathology is unknown. We compared Fc in 91 patients with clinical and EMG evidence of L5 or S1 radiculopathy with Fc in 81 controls in order to evaluate its sensitivity in lumbosacral radiculopathy. F waves were obtained by stimulating the peroneal and tibial nerves behind the knee and recording from the extensor digitorum brevis (L5 predominant) and flexor hallucis brevis (S1 predominant) muscles, respectively. Fc was calculated by subtracting the shortest F wave latency from the longest and, in controls, ranged from 0.2 to 23.4 ms in the peroneal nerve, and from 1.2 to 13.4 ms in the tibial nerve (95th percentile = 13 ms for the peroneal nerve and 9.2 ms for the tibial nerve). In the patient group, Fc also ranged from 0.2 to 23.4 ms in the peroneal nerve, and from 0.4 to 18.2 ms in the tibial nerve. Only 5 (5.5%) and 8 (11.3%) patients for the peroneal and tibial nerves, respectively, had Fc values which fell beyond the 95th percentile, a percentage far below the sensitivity of F wave latency measurement and not substantially different from chance. Thus we conclude that Fc has no substantial additional value in evaluating lumbosacral radiculopathy over that of F wave latency.     

H-reflex to S1-root stimulation improves utility for diagnosing S1 radiculopathy

ObjectiveThe H-reflex on stimulation of the tibial nerve in the popliteal fossa is routinely used in the diagnosis of first sacral (S1) nerve-root radiculopathy. The H-reflex latency, however, is considered to lack sensitivity since a small change from the focal root pathology can be diluted in a relatively long reflex latency. We have studied the soleus H-reflex elicited by stimulation of the S1 nerve root at the S1 foramen. The normal values for the S1-foramen H-reflex have been reported in a previous study, but there are no definitive reports in patients with S1 radiculopathy. This study was undertaken to determine whether stimulating at the S1 nerve root can improve the utility of the H-reflex for detecting an S1-root lesion.MethodsA randomised paired-study design was utilised to evaluate two H-reflexes: one elicited with tibial nerve stimulation and one elicited with S1-root stimulation. Fifty-five patients with unilateral S1 radiculopathy, confirmed by clinical, electrodiagnostic and magnetic resonance imaging (MRI) evidences were studied. A high-voltage electrical stimulator was used to elicit H-reflexes bilaterally at the S1 foramen and L4/L5 spine level. Latencies were compared with previously generated normal values and similar responses from the asymptomatic leg, focussing on the interval between the peak of M- and H-waves (HMI).ResultsOn the symptomatic side, 39 of the 55 patients had abnormal tibial H-reflex latencies and 54 patients had abnormal responses on S1-foramen stimulation (absent in 18; HMI prolonged >0.4 ms in 36). On the asymptomatic side, all 55 patients had normal tibial H-reflexes, and 52 had normal responses on S1-foramen stimulation. In three patients, the HMI was abnormal on S1-foramen stimulation. In 46 patients tested with L4/L5-level stimulation, H-reflex was present in 39 and absent in seven. The latency of the M-wave to S1 stimulation was normal.ConclusionsAbnormal S1-root H-reflexes reveal lesions at the S1 root in patients with normal tibial H-reflexes; therefore, enhancing diagnostic sensitivity. The appearance of the H-reflex to L4/L5-level stimulation in patient with absent H-reflex to S1-foramen stimulation further localises the site of S1 nerve-root lesion to the L5/S1 spine level. Thus, H-reflex to S1-root stimulation significantly increases the diagnostic sensitivity for S1 radiculopathy.SignificanceIn our study, the S1-root H-reflex with high-voltage electrical stimulation has shown greater sensitivity than the tibial H-reflex in evaluating S1 compressive radiculopathies. An abnormal S1-root H-reflex helps to localise the lesion to the S1 root in patients with concurrent abnormal tibial nerve H-reflex, which may increase diagnostic specificity.     

F wave duration in mild S1 radiculopathy: comparison between the affected and unaffected sides.

OBJECTIVES: The aim of this study was to investigate the F wave duration (Fdur) of the tibial nerve in mild S1 radiculopathy. We evaluated the difference in this parameter between the affected and unaffected sides, and discussed the clinical significance of this difference. METHODS: Bilateral tibial F waves were obtained from 46 normal subjects (control group) and 27 patients with L5/S1 intervertebral disc herniation (patient group). Minimum latency of F wave (Fmin) and Fdur were analyzed. RESULTS: Fmin and Fmin corrected by the subject's height (Fmin/H) were both significantly longer on the affected side than on the unaffected side and in the normal group, but the incidence of abnormality was very low for both parameters. Even patient showing normal Fmin or Fmin/H sometimes exhibited Fdur values prolonged beyond the reference range. Judgment of abnormal Fdur based on the difference between the two sides was the most sensitive method for detecting the root injury. No patients showed decreased Fdur. There was no significant difference between the two groups in the amplitude of compound muscle action potential of the abductor hallucis. CONCLUSIONS: Our study suggested that evaluation of the difference in Fdur between the two sides was a valuable means of decreasing false-negative results in F wave study in mild S1 radiculopathy cases.     

Clinical utility of reflex studies in assessing cervical radiculopathy.

We prospectively studied the diagnostic utility of upper limb segmental reflexes in patients with suspected cervical radiculopathy (CR). Fifty-three patients (29 men and 24 women), referred for electrodiagnostic testing, were positive for at least one of four clinical criteria for CR: abnormal (1) history, (2) motor (myotomal) examination, (3) sensory (dermatomal) examination, and (4) changes in deep tendon reflexes (DTR). All underwent electrodiagnostic assessment, needle electrode examination (NEE), specialized segmental reflexes (heteronymous and Hoffman's reflexes [H reflexes]), and neuroimaging. The clinical diagnosis was supported in all 32 patients who entered the study with two or more clinical signs for CR. Abnormal NEE was found in 90% of subjects with three clinical signs, 59% with two signs, and only 10% of those with one sign. H reflexes demonstrated a sensitivity of 72% and specificity of 85% for detection of CR and were particularly helpful when forming conclusions in the 21 subjects with only one clinical sign for CR. Specialized segmental H-reflex studies of the upper limb were as sensitive and specific as neuroimaging (magnetic resonance imaging).     

Diagnostic utility of F waves in cervical radiculopathy: electrophysiological and magnetic resonance imaging correlation

OBJECTIVE: F wave study is a simple, non-invasive method commonly utilized for evaluation of cervical root lesions. Its diagnostic sensitivity is low. There are no large series comparing F wave studies with MRI as a reference standard. PATIENTS AND METHODS: We performed F wave studies in 30 controls (15 men; mean age: 50 years; standard deviation: 17.9 years; range: 21-80 years) and, prospectively, 31 patients (19 men; mean age: 48 years; standard deviation: 16.2 years; range: 26-79 years) referred for evaluation of cervical spondylotic radiculopathy (CSR). All patients' MRIs were compared with F wave parameters. RESULTS: Combined utilization of minimal F latency, F chronodispersion, F persistence and side to side differences resulted in 55% sensitivity and 100% side concordance for detecting CSR, with MRI as a comparison standard. F wave parameters also provided complementary information to needle electromyography in the diagnostic evaluation of CSR. Although F waves were not indicative of radiculopathy levels, 4/31 (13%) of cases had at least one abnormal F wave parameter, despite normal electromyography findings. CONCLUSIONS: Combined utilization of multiple F wave parameters is a useful, diagnostic adjunct in the electrophysiological evaluation of CSR.     

Unilateral calf enlargement following S1 radiculopathy

Two cases of unilateral calf enlargement following S₁ radiculopathy are reported. “True” muscular hypertrophy could be confirmed by computerized tomography of the muscle. Muscle biopsy disclosed that fiber hypertrophy exceeded grouped fiber atrophy. In one case both fiber types were involved, and in the other mostly type 1 fibers were affected. Electromyography revealed dense pseudomyotonic activity and fasciculations. These findings are discussed in view of the current literature.     

The diagnostic sensitivity of different F wave parameters

OBJECTIVE—To examine the relative diagnosticsensitivity of various F wave parameters.
METHODS—Normal values for minimum, mean, andmaximum F wave latency, chronodispersion, and persistence in the fourmajor motor nerves were established and systematically applied to atleast four separate categories of patients (radiculopathies,polyneuropathies, mononeuropathies, and others). F Waves were studiedboth isolated and in comparison with other motor nerve conduction parameters.
RESULTS—F Chronodispersion was the most oftenabnormal parameter, particularly in lumbosacral radiculopathies.Minimum F wave latency was more useful in polyneuropathies. Comparedwith minimum F wave latency, F chronodispersion was able to identifymost additional cases.
CONCLUSIONS—F Wave studies should include minimumF wave latency and chronodispersion.

     

Dermatomal somatosensory evoked potentials in unilateral lumbosacral radiculopathy

We examined scalp-recorded somatosensory evoked potentials (SSEPs) to electrical stimulation of the peroneal nerves and to stimulation in the L5 and S1 dermatomes in 19 patients with unilateral radiculopathies involving these segments. For the dermatomal studies at least two trials of 512 responses were recorded from the vertex with reference to both the midfrontal and contralateral parietal electrodes, using an averaging technique. Findings on the symptomatic and asymptomatic sides were compared in each patient. We found that peroneal SSEPs were normal in all patients. Dermatomal SSEPs correctly identified the lesion in 5 patients. In 1 patient dermatomal SSEPs lateralized the lesion correctly but localized it to the adjacent root. In 10 cases dermatomal SSEPs gave misleading information, indicating an abnormality on the asymptomatic side in 1 patient and no abnormality in 9. In the remaining 3 patients, both SSEPs and radiological contrast studies failed to identify any lesion, although the radiculopathy was confirmed by electromyography. These findings raise doubt about the ultimate utility of these evoked potential techniques in the evaluation of patients with suspected radiculopathies.     

Reference values of F wave parameters in healthy subjects.

OBJECTIVE AND METHODS: A large reference value database for F wave parameters was constructed with data from 121 to 196 healthy subjects; the age range of the subjects was 14-95 years. We studied the following parameters: minimum F wave latency (FMINLAT), mean F wave latency (FMEANLAT), maximum F wave latency (FMAXLAT), number of F waves/20 stimuli (FNUMBER) and F wave dispersion (FDISP=FMAXLAT-FMINLAT). The median, ulnar, peroneal and tibial nerves were studied. RESULTS: Height explains almost half of the FMINLAT variability. The F wave latency increases with height in the arms by 0.2 ms/cm and in legs 0.4 ms/cm. The effect of age on F wave latency in the arms is relatively small, only 0.03 ms/year; and in the legs age increases the FMINLAT by 0.1 ms/year. Gender does not affect FMINLAT in a systematic way. The peroneal nerve has slightly longer FMINLAT than the tibial nerve, while the FNUMBER is higher in the tibial nerve than the peroneal nerve. The differences between the ulnar and median nerve are slight. There is a very high correlation between all 3 latency parameters (FMINLAT, FMAXLAT and FMEANLAT), but no correlation between FDISP and FNUMBER and the other parameters.Side to side comparisons reveals no significant differences in any of the parameters except for the median nerve FMINLAT and FMEANLAT, which is 0.2 ms longer on the right than left. If side difference of more than 2 standard deviation is taken as the upper limit for normal, the side difference in arms is 1.4 ms and in legs 3 ms.In repeated studies the interexaminer variability is small; the correlation coefficient between the different F parameters is high (P>0.6 in arms and P>0.7 in legs). In the arms the upper limit for a significant difference of FMINLAT on repeated studies in the median nerve is 1.0 and 1.7 ms for the ulnar nerve. In the legs, FMINLAT for the peroneal nerve is 2.6 ms and for the tibial nerve is 2.1 ms. CONCLUSIONS: This large reference value database can be used not only to evaluate single measurements in relation with height and age, but also to compare right and left side and changes over time at repeated studies.     

A study of F-waves in patients with unilateral lumbosacral radiculopathy

Background and purpose:  The F wave, a late response of low amplitude, is widely used in the study of peripheral nerve lesions, and its persistence and latencies are the main parameters that are usually considered. The analysis of repeater F-waves, which are commonly observed in association with focal or generalized motor neuropathy, is not always performed as a standard electrodiagnostic protocol.
Methods:  We recorded and quantified the F waves from 13 healthy subjects and 22 patients with unilateral lumbosacral radiculopathy (ULSR) affecting the L5 or S1 roots.
Results:  We found differences between the injured and normal sides of patients with ULSR in several F-wave parameters. Taking into consideration the normalized and pooled values of tibial and peroneal nerves in the injured side of patients with ULSR, the minimum and mean latencies were higher (1.05 and 1.04 with respect to 1.00; P  <   0.01), the relative amplitude of the F waves was higher (1.95 with respect to 1.00; P  <   0.001), and the percentage of repeater F-waves was also higher (4.19 with respect to 1.00; P  <   0.001). This latter parameter was the most sensitive to detect lateral differences as indicated by the percentage of change and its high z score.
Conclusions:  Our results show that the use of F-waves may improve the electrodiagnosis of the ULSR if the number of repeater waves is evaluated given the clear and consistent increase of this variable in patients with lumbosacral root injury.     

Subtypes of carpal tunnel syndrome: median nerve F wave parameters

The carpal tunnel syndrome (CTS) provides a model for analyzing the effects of focal nerve injury on F waves. We studied 127 patients (164 CTS) with clinical and electrophysiological CTS and 35 healthy controls in order to determine the alteration of F wave parameters in different types of CTS and to evaluate the most predictive F wave abnormality for each type. Minimal, maximal and mean F wave latencies, F wave persistence and chronodispersion recorded from abductor pollicis brevis (APB) muscle with wrist stimulation were compared. Twenty-three patients (29 CTS) had prominent demyelinating type CTS, 37 patients (45 CTS) had prominent axonal type CTS and 60 patients (90 CTS) slight demyelinating CTS according to electrophysiological parameters. The amplitude of APB muscle and F wave persistence were correlated significantly (r: 0.36, P<0.001). Minimal F wave latency was more prolonged in demyelinating group than in the axonal and slight demyelinating groups (P=0.001). In conclusion, F wave determination, as a simple and valuable method, allows the discrimination between demyelinating injury and axonal degeneration and increases the diagnostic yield in CTS.     

Clinical and morphological study of calf enlargement following S-1 radiculopathy.

Calf enlargement following sciatica is a rare condition. It is reported the case of a 28-year-old woman who complained of repeated episodes of lower back pain radiating into the left buttock and foot. One year after the beginning of her symptoms, she noticed enlargement of her left calf. X-ray studies disclosed L5-S1 disk degeneration. EMG showed muscle denervation with normal motor conduction velocity. Open biopsies of the gastrocnemius muscles were performed. The left gastrocnemius muscle showed hypertrophic type 2 fibers in comparison with the right gastrocnemius. Electron microscopy showed mildly increased number of mitochondria in these fibers. A satisfactory explanation for denervation hypertrophy has yet to be provided.     

S-1 radiculopathy as a possible predisposing factor in focal myositis with unilateral hypertrophy of the calf muscles.

Associated with chronic S-1 radiculopathy, a 44-year-old man developed unilateral hypertrophy of the calf muscles. Electromyography revealed neurogenic alterations in the corresponding limb compatible with S-1 radiculopathy. In addition, MR-tomographic and bioptic findings were consistent with a focal inflammatory myopathy of the enlarged right gastrocnemius muscle. Predisposing factors for the localisation of a focal myositis are unknown. This case report highlights the diagnostic difficulties in distinguishing focal myositis and denervation hypertrophy following S-1 radiculopathy or secondary inflammation related to denervation. We consider the possibility that in our case the inflammatory process might have been triggered by electromyographically proven chronic denervation related to radiculopathy.     

The importance of sample size for the estimation of F wave latency parameters in the peroneal nerve

We studied the peroneal nerve F waves in 20 healthy subjects and 20 patients with neuropathy to assess the effect of sample size on the accuracy of measurements of the following F wave latency parameters: F wave minimum latency, mean latency, median latency and F chronodispersion. The values obtained from a large sample (65–110 F responses) were compared with the corresponding values from smaller samples of 10, 20 and 40 responses. The results indicated that equally accurate measurements for all parameters were provided by larger F wave samples in patients, compared with healthy subjects. Amongst the various parameters, FchR required the largest and FLmean the smallest sample, in order to achieve results of the same accuracy. A sample of 40 fulfilled the requirements for all F wave latency parameters of the peroneal nerve in almost all subjects, a finding which is in good agreement with that of a similar study for the ulnar nerve.     

Contralateral S1 function is involved in electroacupuncture treatment-mediated recovery after focal unilateral M1 infarction

Acupuncture at acupoints Baihui(GV20)and Dazhui(GV14)has been shown to promote functional recovery after stroke.However,the contribution of the contralateral primary sensory cortex(S1)to recovery remains unclear.In this study,unilateral local ischemic infarction of the primary motor cortex(M1)was induced by photothrombosis in a mouse model.Electroacupuncture(EA)was subsequently performed at acupoints GV20 and GV14 and neuronal activity and functional connectivity of contralateral S1 and M1 were detected using in vivo and in vitro electrophysiological recording techniques.Our results showed that blood perfusion and neuronal interaction between contralateral M1 and S1 is impaired after unilateral M1 infarction.Intrinsic neuronal excitability and activity were also disturbed,which was rescued by EA.Furthermore,the effectiveness of EA treatment was inhibited after virus-mediated neuronal ablation of the contralateral S1.We conclude that neuronal activity of the contralateral S1 is important for EA-mediated recovery after focal M1 infarction.Our study provides insight into how the S1-M1 circuit might be involved in the mechanism of EA treatment of unilateral cerebral infarction.The animal experiments were approved by the Committee for Care and Use of Research Animals of Guangzhou University of Chinese Medicine(approval No.20200407009)April 7,2020.     

Clinical utility of the judgment of line orientation test and facial recognition test in children with acquired unilateral cerebral lesions.

In unselected adult patients with brain damage, the Judgment of Line Orientation Test and the Facial Recognition Test are considered valid instruments for detecting right cerebral hemisphere lesions. It is unknown, however, whether this applies to children as well. Performance levels on the Judgment of Line Orientation Test and the Facial Recognition Test of 18 children with acquired left cerebral lesions and 14 children with acquired right cerebral lesions were reviewed. Subjects were unselected for age, sex, or etiology. Age-related norms were obtained in 81 normal controls, aged 7 to 14 years. Judgment of Line Orientation Test and Facial Recognition Test performance levels did not predict the presence of cerebral pathology per se in our unselected groups with demonstrated unilateral cerebral lesions, nor did they contribute to the prediction of the side of the lesion within the two groups with cerebral lesions. These results cast serious doubt on an important aspect of the clinical utility of both tests in children, namely their discriminative validity in the assessment of etiologically unselected populations with brain damage.     

Hypertrophy of the calf with S-1 radiculopathy

Occasionally, chronic denervation is associated with enlargement rather than atrophy of muscle tissue. We studied seven patients with S-1 radiculopathy who developed ipsilateral enlargement of the calf. On the basis of results of calf muscle biopsies, it seems likely that the enlargement was due to muscle fiber hypertrophy and atrophy combined with an increase in connective tissue. Computed tomograms of the legs revealed no evidence of tumor. Surgical decompression of the involved S-1 nerve root had no obviously beneficial effect in reducing the calf enlargement. More information is needed to define the natural course of the calf enlargement and to clarify the pathophysiologic processes involved.