Terminal latency index and modified F ratio in distinction of chronic demyelinating neuropathies.

OBJECTIVE: To evaluate indexes calculated from standard electrophysiological data in differentiating chronic demyelinating polyneuropathy (CDP). METHODS: Nerve conduction study of upper limbs was investigated in 19 chronic inflammatory demyelinating polyneuropathy (CIDP) patients, 25 anti-myelin-associated glycoprotein/sulfated glucuronyl paragloboside antibodies (MAG/SGPG) CDP patients, 13 Charcot-Marie-Tooth disease type 1A (CMT1A) patients and 22 controls. Terminal latency index (TLI) was used to compare the wrist-to-thenar muscle segment with the elbow-to-wrist conduction velocity. Modified F ratio (MFR) was used to compare the spinal cord-to-elbow segment latency with that of the wrist-to-thenar muscle segment. RESULTS: Compared with controls, TLI was decreased in 21 anti-MAG/SGPG CDP patients while MFR was either decreased or was normal. In 16 CIDP patients, MFR was increased while TLI was either normal or increased. In CMT1A both TLI and MFR were in normal ranges. The sensitivity of MFR as a supportive finding in CIDP was found to be 84% and its specificity 89%. The sensitivity of TLI as a mean of diagnosis of anti-MAG/SGPG CDP was found to be 93% and its specificity 90%. CONCLUSIONS: The results of TLI and MFR facilitates distinction between different types of CDP. In CIDP, MFR was significantly higher and TLI showed no change; in the anti-MAG/SGPG CDP, TLI and MFR were significantly lower; in CMT1A, TLI and MFR showed no change in comparison with the controls.     

Motor conduction parameters in neuropathies associated with anti-mag antibodies and other types of demyelinating and axonal neuropathies

We measured residual latency (RL), motor conduction velocity (MCV), and terminal latency index (TLI) in 15 patients with neuropathy and anti-MAG or SGPG antibodies and compared these to values obtained in 103 patients with other types of polyneuropathy (PN) and to 57 normal subjects. Ten patients had anti-MAG antibody titers of 25,600 or higher, and 5 had titers between 800 and 12,600. Patients with the highest titers had longer RL, slower MCV and shorter TLI than those with lower titers, acute or chronic inflammatory demyelinating PN, hereditary neuropathy, and metabolic or axonal neuropathy. In contrast F-wave latencies did not contribute to the differentiation between the groups of demyelinating neuropathies. RL and TLI correlated best with anti-MAG antibody titers, whereas there was a poor correlation with anti-SGPG titers suggesting that MAG more than SGPG may be the antigen in PN, and that the distal nerves are affected more than their proximal segments. The RL rather than TLI turned out to be the best variable to classify the demyelinating type of anti-MAG neuropathy. Sural nerve biopsy in 5 of the patients with the highest titer of anti-MAG antibodies showed deposits of lgM and C3 on the myelin sheaths, pronounced demyelination and widening of the myelin lamellae. In 4 of the patients with lower titers demyelination was absent or less pronounced. © 1995 John Wiley & Sons, Inc.     

Distal motor latency and residual latency as sensitive markers of anti-MAG polyneuropathy

There is debate whether the terminal latency index (TLI) is a sensitive marker for polyneuropathy with anti-myelinassociated-glycoprotein antibodies (anti-MAGP). We examined 6 patients with an anti-MAGP and 6 patients with a chronic inflammatory demyelinating polyneuropathy (CIDP). The electroneurographic features studied were: distal compound motor action potential (CMAP), distal motor latency (DML), motor conduction velocity (MCV) elbow to wrist (distal MCV), MCV axilla to elbow (proximal MCV), MCV distal/proximal, terminal latency index (TLI), residual latency (RL), F-wave, and modified F ratio.We found significant differences between anti-MAGP and CIDP for DML and for RL.No significant differences were found for TLI and the other measures. The TLI values were not significant probably because our patients had a longer duration of disease,which supports the hypothesis of a distal to proximal progression of conduction slowing over time. We propose that a residual latency >4.0 and a distal motor latency >7.0 are strongly suggestive for an anti- MAGP.     

COMPARATIVE NEUROPHYSIOLOGICAL STUDY FOR THE DIAGNOSIS OF MILD POLYNEUROPATHY IN PATIENTS WITH DIABETES MELLITUS AND GLUCOSE INTOLERANCE

This article evaluates diagnostic sensitivity of minimal F-wave latency, sural/radial amplitude ratio (SRAR), dorsal sural/radial amplitude ratio (DSRAR), sympathetic skin response (SSR), and R-R interval variability (RRIV) for detecting early polyneuropathy in patients with glucose intolerance and diabetic patients. F-wave latencies were more prolonged in diabetic patients with normal and abnormal nerve conduction studies than control subjects (p < .001). SRAR was lower, SSR latency was more prolonged, and RRIV was lower in diabetic patients with abnormal nerve conduction studies than healty controls (p < .001). SSR latency was more prolonged and RRIV was lower in diabetic patients with normal nerve conduction studies than healty controls (p < .01, p < .05, respectively). DSRAR was lower in diabetic patients with normal and abnormal nerve conduction studies than control subjects (p < .001). DSRAR was also lower in patients with glucose intolerance than control subjects (p < .01). DSRAR was the most sensitive and specific test in either of diabetic patients with normal nerve conduction studies (sensitivity 66%, specificity 90%) and diabetic patients with abnormal nerve conduction studies (sensitivity 100%, specificity 90%). DSRAR is the most reliable method for detection of early nerve pathology. Patients with glucose intolerance might have subclinical neuropathy that can be demonstrated with DSRAR analysis.     

Clinical utility of dorsal sural nerve conduction studies in healthy and diabetic children.

OBJECTIVE: Monitoring of the dorsal sural sensory nerve action potential (SNAP) is a sensitive method for detection of peripheral neuropathies. We tried to determine the normal dorsal sural nerve conduction values of the childhood population and assessed the clinical utility of this method in diabetic children who have no clinical sign of peripheral neuropathy. METHODS: In the study, 36 healthy and 27 diabetic children were included. In all subjects peripheral motor and sensory nerve studies were performed on the upper and lower limbs including dorsal sural nerve conduction studies. RESULTS: The dorsal sural SNAP mean amplitude was 8.24+/-3.08 microV, mean latency was 2.47+/-0.48 ms, mean sensory conduction velocity was 41.63+/-5.43 m/s in healthy children. Dorsal sural SNAPs were absent bilaterally in one diabetic patient. In the other 26 diabetic patients, the mean dorsal sural nerve distal latency was longer (2.93+/-0.63 ms, P = 0.004), mean SCV was slower than in healthy subjects (36.68+/-7.66 m/s, P = 0.005). However, dorsal sural nerve amplitude was not different between the groups. A dorsal sural nerve latency of more than 2.9 ms had a sensitivity of 50% and a specificity of 75%. A dorsal sural nerve velocity of less than 36 m/s had a sensitivity of 54% and a specificity of 92%. CONCLUSIONS: We designated the reference values of the dorsal sural nerve in healthy children. In addition, our findings suggest that dorsal sural nerve conduction studies may have value to determine neuropathy in the early stages in children with diabetes. SIGNIFICANCE: The dorsal sural nerve conduction studies in diabetic children may have value to determine the neuropathy in its early stages.     

交感皮肤反应对糖尿病自主神经病变的诊断价值

目的探讨交感皮肤反应（sympathetic skin response,SSR）在糖尿病自主神经病变诊断中的价值。方法对186例糖尿病周围神经病（Diabetic peripheral neuropathy,DPN）患者和203例糖尿病非DPN患者进行SSR检测,同时对102例健康人进行SSR检测。结果SSR起始潜伏期异常率高于波幅异常率,下肢的异常率高于上肢异常率。DPN患者中,174例（93.5%）SSR异常,其中32例未引出SSR,142例起始潜伏期延长,109例波幅下降。203例DM非DPN患者中,46例（22.7%）SSR起始潜伏期延长和/或波幅下降,其中19例有出汗异常,4例在检查后数月出现出汗异常。结论SSR是早期诊断糖尿病自主神经病变的敏感手段,可发现亚临床神经病,并与病情进展相吻合。     

Visual evoked responses in hereditary motor and sensory neuropathies

The P2 latency of the pattern reversal visual evoked response was measured in 11 patients with hereditary motor and sensory neuropathy (HMSN). The P2 latency was inversely related to the peripheral nerve conduction velocity, but no significant relation was found between the P2 latency and the age of the patients or the duration of their symptoms. When the whole group was considered the mean P2 latency was longer but not significantly different from a control group. When the 11 patients were differentiated into HMSN I (5 males) and HMSN II (2 females, 4 males) the P2 latencies of the patients with HMSN I were significantly longer than those with HMSN II. The data support earlier findings that subclinical involvement of the optic nerve may occur in HMSN and suggest that measurement of P2 latency may be of value in the differentiation of HMSN. More than two subtypes, however, may exist.     

Comparative neurophysiological study for the diagnosis of mild polyneuropathy in patients with diabetes mellitus and glucose intolerance

This article evaluates diagnostic sensitivity of minimal F-wave latency, sural/radial amplitude ratio (SRAR), dorsal sural/radial amplitude ratio (DSRAR), sympathetic skin response (SSR), and R-R interval variability (RRIV) for detecting early polyneuropathy in patients with glucose intolerance and diabetic patients. F-wave latencies were more prolonged in diabetic patients with normal and abnormal nerve conduction studies than control subjects (p < .001). SRAR was lower, SSR latency was more prolonged, and RRIV was lower in diabetic patients with abnormal nerve conduction studies than healty controls (p < .001). SSR latency was more prolonged and RRIV was lower in diabetic patients with normal nerve conduction studies than healty controls (p < .01, p < .05, respectively). DSRAR was lower in diabetic patients with normal and abnormal nerve conduction studies than control subjects (p < .001). DSRAR was also lower in patients with glucose intolerance than control subjects (p < .01). DSRAR was the most sensitive and specific test in either of diabetic patients with normal nerve conduction studies (sensitivity 66%, specificity 90%) and diabetic patients with abnormal nerve conduction studies (sensitivity 100%, specificity 90%). DSRAR is the most reliable method for detection of early nerve pathology. Patients with glucose intolerance might have subclinical neuropathy that can be demonstrated with DSRAR analysis.     

Subclinical neuropathy in type I diabetic children

Objectives: Small and large, somatic and autonomic nerve fibre functions were neurophysiologically evaluated in 33 asymptomatic neurologically free type 1 diabetic children and 69 age-matched healthy controls. Methods: The evaluation of large and small somatic nerve fibre function was performed by conventional nerve conduction studies, thermal specific and thermal pain sensitivity tests, as well as autonomic nerve fibre functions by sympathetic skin response and R–R interval variation assessment. Results: A significant difference was established between the healthy and the diabetic group. Neurophysiologically determined subclinical neuropathy was found in 87% of type 1 diabetic children. The majority of abnormal recordings were found on the lower limbs. The dysfunction of the somatic motor large nerve fibre type in the lower limbs was altered in 57% of patients, somatic sensory large in 39%, somatic sensory small in 45%, and sympathetic in 45%. The leading abnormal measure was a delayed sympathetic skin response on the foot (42% of diabetic children) followed by a reduced amplitude of sural nerve action potential (36%). The whole spectrum of recordings showed scattered involvement of nerve functions. There was no selective susceptibility of nerve fibre types exposed to a noxious factor. Conclusion: A complex neurophysiological assessment, including standard nerve conduction studies as well as psychophysical examination and autonomic nerve function tests, evaluating the function of small and large nerve fibres, is recommended for evaluating the subclinical neuropathy in asymptomatic type I diabetic children.     

Electroneurographic investigations of misonidazole polyneuropathy.

13 patients with malignant tumors were treated by the radiosensitizer misonidazole (Ro 07-0582), total dosage 20-29 g. The electrophysiological investigations showed (1) an early increase of distal latency, the motor nerve conduction velocity (NCV) of the peroneal nerve and the NCV of the sural nerve remaining normal or only signlty reduced, and in a few cases a marked reduction of the compound action potential or of the nerve action potential (NAP), indicating a primary axonal neuropathy; (2) greater changes in the parameters of sensory nerves (n. suralis) than of motor nerves; (3) the distal latency is a good indicator of subclinical neuropathies; (4) the electrophysiological parameters showed a normalization 6 months after the end of therapy. The mechanisms possibly responsible for the misonidazole neuropathy are discussed.     

POEMS综合征神经传导异常分析

目的 阐明POEMS综合征的电生理特点.方法 对比分析22例POEMS综合征与22例慢性炎症性脱鞘性多发性神经根神经病(CIDP)患者的电生理资料.结果 POEMS组运动神经传导速度(MNCV)较CIDP组减低,但差异无统计学意义(P＞0.05);远端运动潜伏期(DML)明显减低,远端潜伏期指数(TLI)明显增高,差异均有统计学意义(P均＜0.05);POEMS组神经传导阻滞出现率较CIDP组低,差异有统计学意义(P＜0.05);POEMS组胫神经复合肌肉动作电位(CMAP)较CIDP组减低,差异有统计学意义(P＜0.05),而正中神经两组差异无统计学意义(P＞0.05);POEMS组下肢肌异常肌电出现率较上肢高,差异有统计学意义(P＜0.05).结论 POEMS综合征神经传导速度减慢主要在周围神经中间部分,传导阻滞出现率低,神经传导异常可能与上下肢体有关.     

The median nerve terminal latency index in carpal tunnel syndrome: a clinical case selection study.

The terminal latency index (TLI) adjusts the distal motor latency (DL) for the terminal distance and the proximal nerve conduction velocity. We prospectively studied 66 patients in order to assess the sensitivity of the median nerve TLI for the diagnosis of carpal tunnel syndrome (CTS). Clinical and electrophysiological evaluations were completed by separate, blinded examiners. Based on the clinical diagnosis, 54 patients were judged to have CTS (CTS group) and 12 were believed not to have CTS. Control data were obtained from 38 healthy hands. The mean TLI was 0.26 +/- 0.04 in the CTS group and 0.43 +/- 0.04 in the control group (P < 0.001). The sensitivity of the TLI was 81.5%. The TLI was statistically better than the median motor DL and sensory peak latency (PL) to the second digit. The TLI was always abnormal when the median mixed-nerve palmar latency was abnormal. In three cases from the CTS group, the TLI was the only abnormal electrophysiological parameter. The median TLI is a useful, sensitive electrodiagnostic parameter for CTS.     

Electrophysiological studies in diabetic neuropathy

In 30 patients with diabetic neuropathy sensory potentials in the median nerve, motor conduction in the lateral popliteal and median nerves, and electromyographic findings in distal and proximal muscles were compared with the severity of symptoms and signs. All patients had abnormalities in at least one of the electrophysiological parameters. The sensory potentials were the most sensitive indicator of subclinical involvement; abnormalities were found in 24 patients, 12 of whom had no sensory symptoms or signs and five of whom had no other clinical or electrophysiological evidence of neuropathy in the upper extremities. This indicates that sensory nerve fibres may be affected before motor. The next most sensitive parameter was the presence of fibrillation potentials, found in more than half the distal muscles examined. Slowing in motor conduction in the lateral popliteal nerve was the only electrophysiological change correlated to the severity of the neuropathy, and no other electrophysiological parameter was correlated to the duration or the severity of the neuropathy or the diabetes. An onset of neuropathy before or simultaneously with the manifestations of the diabetes, as well as the frequent occurrence of asymptomatic changes in sensory conduction, support the evidence at hand that the neuropathy develops concomitantly with and as an integral part of the metabolic disturbance rather than as a consequence of the vascular complications of diabetes. Of three patients with clinical signs or symptoms of a diabetic amyotrophy, two had asymptomatic electrophysiological abnormalities in distal nerves and muscles, consistent with widespread involvement of the peripheral nerves. The third patient had electromyographic changes in the medial vastus muscles suggestive of a myopathy. Motor and sensory conduction in distal and proximal nerves were normal.     

糖尿病周围神经病97例临床特征与神经电生理分析

目的:探讨糖尿病周围神经病(DPN)患者的临床特征与神经电生理变化。方法:分析97例DPN患者的临床特征,比较DPN组和对照组的神经传导速度(NCV)、远端潜伏期、远端波幅3个参数。结果:①临床特征以肢体麻木(59%)最多见、其次为疼痛(42%)。②患者组NCV、远端波幅值低于对照组,远端潜伏期比对照组延长;两组3个参数比较,除腓总神经远端波幅、尺神经感觉传导速度和正中、尺、腓肠神经远端潜伏期外,差异均有统计学意义(P<0.05)。结论:①DPN患者临床特征以肢体麻木和疼痛最多见;②检测NCV、远端潜伏期、远端波幅,能较早发现临床患者。     

Clinical–neurophysiological correlations in a series of patients with IgM-related neuropathy

ObjectiveWe aim to draw clinical–neurophysiological correlations in our cohort of patients affected by IgM-related neuropathy to investigate whether neurophysiological parameters may help differentiate the classical phenotype from atypical forms.MethodsWe retrospectively evaluated patients with IgM-related neuropathy referred to our Institute from 1990 to 2011. All patients underwent extensive laboratory, clinical and neurophysiological evaluation.ResultsA classic sensory-ataxic form was observed in 20 of 34 patients, while an atypical phenotype (multiple mononeuropathy, polyneuropathy with predominant motor impairment, painful small-fibre neuropathy) was identified in the remaining 14 cases. Nerve conduction studies revealed in almost all cases a pattern typical of demyelination.A reduced terminal latency index and a prolonged distal motor latency of median nerve, as well as a prolonged distal motor latency and a reduced motor conduction velocity of peroneal nerve when recorded from extensor digitorum brevis, were significantly associated with classic sensory-ataxic phenotype. Conversely, a compound muscle action potential amplitude reduction of peroneal nerve from the tibialis anterior, was mostly associated with atypical forms.ConclusionsNo clear electrophysiological differences between classical forms and atypical cases can be identified in IgM-related neuropathy. Still, we demonstrated that demyelinating abnormalities are more often associated with classical phenotypes, while axonal impairment occurs more often in atypical clinical patterns.SignificancePerforming correlations between clinical and neurophysiological findings in IgM-related neuropathy may help to better understand different disease mechanisms in this heterogeneous form of inflammatory neuropathy.     

Reversible peripheral neuropathy in idiopathic hypoparathyroidism

We describe a 40-year-old male with idiopathic hypoparathyroidism presenting with tetany, proximal weakness, signs of hypocalcaemia including Chvostek and Trousseau's and diminished tendon reflexes in the upper and lower limbs. Electrophysiological studies revealed a sensory-motor neuropathy, predominantly axonal as evidenced by decreased CMAP amplitudes, with normal distal latencies-velocites, except for median nerve where a prolonged distal latency was observed. Serial nerve conduction studies were performed at repeated intervals for 2 years, while he received treatment for hypoparathyroidism (calcium and vitamin D supplementation). A progressive improvement in neuropathy both clinical and on electrophysiological studies was observed. Occurrence of peripheral neuropathy in hypocalcaemic states such as hypoparathyroidism and its reversibility after normalization of calcium homeostasis lend proof to the role of critical Ca2+ ion concentration in the normal functioning of the peripheral axons.     

Terminal latency index in polyneuropathy with IgM paraproteinemia and anti-MAG antibody

Criteria for the diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) are met by the polyneuropathy associated with immunoglobulin M (IgM) paraproteinemia and anti-myelin-associated glycoprotein (MAG) antibody (MAG-CIDP). However, MAG-CIDP differs from other types of CIDP, mainly in its poorer response to treatment. The utility of terminal latency index (TLI) as an electrophysiological marker for MAG-CIDP has been debated. In this study we confirmed its diagnostic usefulness and evaluated TLI threshold values for motor nerves investigated in routine nerve conduction studies. Median, ulnar, peroneal, and tibial TLIs of 11 subjects with MAG-CIDP, 18 with CIDP, and 76 healthy controls were compared, and threshold values for MAG-CIDP evaluated as the lowest value with a likelihood ratio higher than 10. Mean TLI values and TLIs of all but the peroneal nerve were significantly lower in MAG-CIDP. Median nerve TLI of 0.26 and ulnar nerve TLI of 0.33 were identified as the threshold TLI values for MAG-CIDP.     

糖尿病前期周围神经病的神经电生理研究

目的 探讨神经电生理(神经传导、F波及皮肤交感反应)检查对糖尿病前期周围神经病的诊断价值。方法 选取100例糖尿病前期患者、50例糖尿病患者及50例健康志愿者,糖尿病前期患者又分为糖耐量异常及空腹血糖受损组,分别为55例及45例; 对上述对象进行四肢神经传导(Nerve conduction studies, NCS)、F波、皮肤交感反应(Skin sympathetic response,SSR)检查。结果(1)糖耐量异常组正中神经感觉动作电位(Sensory nerve active potential,SNAP)、胫后和腓总神经SNAP及感觉传导速度(Sensory nerve conduction velocity,SCV)均低于正常对照组及空腹血糖受损组,空腹血糖受损组腓总神经SNAP、胫后神经SCV均低于正常对照组(P均<0.05);(2)空腹血糖受损组、糖耐量异常组上肢及下肢SSR波幅均低于正常对照组(P均<0.05),糖耐量异常组下肢SSR波幅低于空腹血糖受损组(P均<0.05);(3)糖耐量异常组F波、感觉神经NCS,SSR异常的比例多于正常对照组,空腹血糖受损组SSR异常比例多于正常对照组,糖耐量异常组感觉神经NCS异常的比例多于空腹血糖受损组(P均<0.05)。结论 糖尿病前期患者存在周围有髓鞘大感觉神经纤维及无髓鞘小神经纤维损害,其中糖耐量异常患者周围神经损害重于空腹血糖受损患者,电生理检查以感觉神经NCS及SSR异常为主,利用神经电生理技术利于其周围神经损害的早期诊断。     

Terminal latency index in neuropathy with antibodies against myelin-associated glycoproteins

Neuropathy with antibodies against myelin-associated glycoproteins (MAG/SGPG-N) and hereditary sensorimotor neuropathy type 1 (HMSN1) are characterized by chronic demyelination with little conduction block. Electrodiagnostic studies suggest that in HMSN1 conduction slowing occurs uniformly along the nerve, whereas in MAG/SGPG-N it is predominantly distal. Some but not all previous reports have shown that the terminal latency index (TLI) was useful to distinguish MAG/SGPG-N from chronic idiopathic demyelinating polyneuropathy. We compared median TLI from 21 patients with MAG/SGPG-N with those obtained from 26 patients with HMSN1, 20 with HMSN2, and 12 healthy volunteers. All patients with TLI <0.26 had MAG/SGPG-N, and all patients with TLI > or =0.32 had HMSN1. In the remaining patients with intermediate TLI values, ulnar distal motor latency (DML) aided in differentiation between MAG/SGPG-N and HMSN1 with an overall sensitivity of 100% and specificity of 98%. In conclusion, median TLI in combination with ulnar DML can further guide the demyelinating neuropathy evaluation toward hereditary or autoimmune causes.     

标准化F波潜伏期对糖尿病周围神经病的诊断价值

目的 探讨标准化F波潜伏期在糖尿病周围神经病(DPN)中的诊断价值.方法 采用前瞻性研究方法 ,收集神经传导检查正常的DPN患者48例,另选择年龄和性别匹配的健康自愿者48名为对照组.采用肌电图诱发电位仪检测两组正中神经、尺神经、胫神经及腓总神经F波最短潜伏期(FLmin)、F波平均潜伏期(FLmean)、F波潜伏最长...