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Journal of the Peripheral Nervous System 11:247–252 (2006)RESEARCH REPORT         Dorsal sural nerve conduction study in v...
Turgut et al.                                                          Journal of the Peripheral Nervous System 11:247–252...
Turgut et al.                                                            Journal of the Peripheral Nervous System 11:247–2...
Turgut et al.                                                                    Journal of the Peripheral Nervous System ...
Turgut et al.                                                           Journal of the Peripheral Nervous System 11:247–25...
Turgut et al.                                                                    Journal of the Peripheral Nervous System ...
La conduzione del nervo surale dorsale in pazienti con carenza di vitamina B12 associata ad anemia megaloblastica
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La conduzione del nervo surale dorsale in pazienti con carenza di vitamina B12 associata ad anemia megaloblastica

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La conduzione del nervo surale dorsale in pazienti con carenza di vitamina B12 associata ad anemia megaloblastica

  1. 1. Journal of the Peripheral Nervous System 11:247–252 (2006)RESEARCH REPORT Dorsal sural nerve conduction study in vitamin B12 deficiency with megaloblastic anemia BurhanTurgut1, NildaTurgut2 , Seval Akpinar1, Kemal Balci2 , Gu lsu m E. Pamuk1, « « EmreTekgu ndu z1, and Muzaffer Demir1 « « 1Department of Medicine, Division of Hematology; and 2Department of Neurology, Trakya Medical Faculty, University of Trakya, Edirne, Turkey Abstract Peripheral neuropathy is frequently observed in B12 deficiency. In spite of this, there is little knowledge about peripheral neuropathy in B12 deficiency because the severity of clinical involvement of the central nervous system clearly outweighs signs and symptoms due to peripheral nervous system involvement. We primarily investigated peripheral neuropathy with dorsal sural conduction study, which is a new method for detection of early peripheral neuropathy, in B12 deficiency with megaloblastic anemia. Conventional nerve conduction studies and tibial sensory-evoked potential (SEP) recording were also performed. Twenty-eight B12-deficient patients (15 male, 13 female, mean age 65.8 years) with megaloblastic anemia and 18 age- and sex-matched controls were included in the study. Although dorsal sural sensory nerve action potentials (SNAPs) were not recorded in 15 (54%) of 28 patients, only 9 (32%) of them were found to have poly- neuropathy by conventional conduction studies. Furthermore, patients with dorsal sural SNAP had mean lower amplitude, mean longer latency, and slower velocity response when compared with controls. Twenty patients (71%) were diagnosed as having myelop- athy by the combination of tibial SEP and neurological findings. Two patients whose dor- sal sural SNAPs were not recorded had normal tibial SEP responses; therefore, these patients were considered to have isolated peripheral neuropathy. As a result, we conclude that dorsal sural nerve conduction study is a reliable method for detection of early periph- eral neuropathy in B12 deficiency. Key words: B12 deficiency, dorsal sural nerve, peripheral neuropathy, SEPIntroduction the central nervous system (Carmel, 2003). Peripheral nerves, however, tend to show axonal degeneration Vitamin B12 deficiency is a systemic disease that without demyelination (McCombe and McLeod,often affects the nervous system. It may cause 1984; Tomoda et al., 1988). Peripheral neuropathy,peripheral neuropathy and lesions in the posterior and which is usually sensory, may be sensorimotorlateral columns of the spinal cord and in the cerebrum (Hemmer et al., 1998), and posterior column damage(Toh et al., 1997). Demyelination with subsequent is often hard to differentiate clinically (Steiner et al.,axonal disruption and gliosis can affect all parts of 1988; Healton et al., 1991). In peripheral neuropathies, the most distal sen- sory fibers of the lower extremities are generally firstAddress correspondence to: Burhan Turgut, MD, Department of affected, but these nerves cannot be evaluated byHematology, Trakya Medical Faculty, University of Trakya, 22030Edirne, Turkey. Tel: þ90 532 433 36 76; Fax: þ90 284 235 76 52; sural and superficial peroneal conduction studies, whichE-mail: burhanturgut@trakya.edu.tr are used routinely for the diagnosis of polyneuropathyª 2006 Peripheral Nerve Society 247 Blackwell Publishing
  2. 2. Turgut et al. Journal of the Peripheral Nervous System 11:247–252 (2006)(Killian and Foreman, 2001). Dorsal sural nerve of the and stimulation was delivered at the wrist and at thefoot is the most distal sensory nerve. It has been elbow. Tibial and common peroneal nerve CMAPsreported that dorsal sural nerve conduction study is were recorded from the abductor hallucis and exten-a sensitive marker of peripheral neuropathies that sor digitorum brevis muscles, and stimulation wasmay show abnormalities before they are found in delivered at the ankle and at the poplitea for tibialproximal sural nerve (Lee et al., 1992; Killian and nerve and at the fibula head for the peroneal nerve.Foreman, 2001; Turgut et al., 2004). Median and ulnar sensory nerve action potentials In this study, we investigated peripheral neuropa- (SNAPs) were recorded with ring electrodes from digitthy by dorsal sural nerve conduction studies in addition 2 and digit 5, and stimulation was applied at the wrist.to conventional conduction studies in B12-deficient Sural antidromic sensory nerve conduction studiespatients with megaloblastic anemia. Also, because were performed by recording the SNAP posterior toposterior column involvement is the most frequently the lateral malleolus. Stimulation was carried out 14reported and complicated neuropathy in B12 defi- cm proximally in the midcalf (Oh, 1993).ciency, tibial sensory-evoked potentials (SEPs) were Filter settings were 20–2,000 Hz bandpass forstudied in all patients. sensory nerve studies, and 2–10,000 Hz bandpass for motor nerve studies. An average was used for the sensory nerve recording, and the mean number of averages required to clearly define the potential wasMaterials and Methods 8. The averaging was repeated to confirm the repro- ducibility, if necessary. In patients whose sensorySubjects nerve response could not be obtained, the averaging The study was carried out between December was repeated at least three to five times. Limb tem-2004 and October 2005. Twenty-eight consecutive perature was maintained between 31 and 34°C in allpatients and 18 healthy age- and sex-matched con- subjects. Polyneuropathy was diagnosed on the basistrols were included in the study. Informed consent of abnormal nerve conduction studies when abnor-was obtained from each subject. The patients met all malities were found in two or more nerves (Feldmanthe following criteria: the presence of megaloblastic et al., 1994).anemia with characteristic features such as macroova-locytosis and hypersegmentation and evidence of Dorsal sural nerve recordingcobalamin deficiency based on a low serum cobalamin Surface bar recording electrodes (Teca Corp.)level (,200 ng/l). were used to test dorsal sural nerve SNAP. A record- All the patients underwent detailed general and ing electrode was placed over the lateral dorsal sur-neurological examination. Routine blood chemistry, face of the foot, with the distal electrode at the origincomplete blood cell count, vitamin B12 analysis, and of digits 4 and 5 and the proximal active electrodefolate serum concentration analysis were performed 3 cm from the distal electrode. The stimulation sitein all patients. Blood smears were examined by was posterior to the lateral malleolus, with the cathodea hematologist. They also had no history of folate placed 14 cm proximal from the recording electrode.deficiency and other spinal cord or peripheral nerve A ground electrode was placed on the dorsum of thediseases. Patients with carpal tunnel syndrome, foot equidistant between the recording and the stimu-radiculopathy, plexopathy, and mononeuropathy were lating electrodes. Low filters were set at 20 Hz andexcluded from the study. Diabetes mellitus, uremia, high filters at 2 kHz. Sweep speed was 1 ms per divi-alcohol abuse, drug use, and other possible causes sion, sensitivity was adjusted between 5 and 20 mVof polyneuropathy were excluded by blood chemistry per division, and stimulus duration was 0.2 ms atanalysis and history of the patients. a stimulus rate of 0.5 Hz. At least eight potentials were averaged to record an appropriate response,Electrophysiological investigations and the averaging was repeated if necessary. DistalConventional motor and sensory nerve latency was measured from stimulus onset to theconduction studies negative peak of the SNAP. SNAP amplitudes were In all patients and control subjects, left median, measured from baseline to peak (Killian and Foreman,ulnar, common peroneal and tibial motor nerves and 2001). A representative figure demonstrating sural andleft median, ulnar, sural sensory nerves were studied dorsal sural nerves action potentials is shown in Fig. 1.with a Medelec Synergy electromyography machine.Median and ulnar nerve compound muscle action Tibial somatosensory-evoked potential recordingpotentials (CMAPs) were recorded from the abductor The active electrode was placed at the Cz0 (2 cmpollicis brevis and the abductor digiti minimi muscles, posterior to Cz). The reference electrode was placed 248
  3. 3. Turgut et al. Journal of the Peripheral Nervous System 11:247–252 (2006) Results Clinical evaluations Clinical and laboratory data of the patients are shown in Table 1. All the patients had a B12 serum level less than 200 pg/ml and obvious megaloblastic anemia. We did not perform a schilling test or intrinsic factor antibody test for diagnosis of pernicious anemia, but eight patients underwent endoscopy and all had type A atrophic gastritis. Moreover, gastrectomy, malabsorption syndromes, vegetarianism, and other rare causes of B12 deficiency were absent in all the patients; therefore, the diagnosis of pernicious anemia in our patients had a high probability. Electrophysiological findings The results of conventional nerve conduction studies of the patients and control subjects are shown in Table 2. Conventional nerve conduction was impaired in 9 (32%) of 28 patients; 4 patients had axonal sensory polyneuropathy, 4 had axonal sensori- motor polyneuropathy, and 1 had mixed (axonal and demyelinating) sensorimotor polyneuropathy. Dorsal sural nerve conduction studiesFigure 1 The top traces show the sensory-evoked poten- . The patients and control subjects underwent dor-tial (SEP) from sural nerve and the bottom traces show the sal sural nerve conduction studies. Dorsal sural nerveSEP from dorsal sural nerve of a control subject. was recordable bilaterally in all the control subjects. Dorsal sural nerve SNAPs were bilaterally absent inat Fpz0 (2 cm behind Fp). The ground electrode was 15 (54%) of 28 patients, and 9 of them had impairedplaced as close to the first pair of recording electrodes. conventional conduction abnormalities simultaneously.With the patient in the supine position, surface stimu- In the other 13 (46%) patients, the mean distal latencylating electrodes were placed behind the medial mal- of the dorsal sural nerve response was longer (p ¼leolus. The exact point of stimulation was identified 0.003), mean amplitude was lower (p ¼ 0.008), andby measuring 1 cm behind and 1 cm below the navic- mean velocity response was slower (p ¼ 0.001) thanular tubercle (medial side of the foot). This point ap- those of 18 healthy controls (Table 3). However, theproximates the middle of the belly of the abductorhallucis muscle. Next, measure 8 cm proximal to thispoint, following the course of the tibial nerve 1 cm Table 1 Clinical and laboratory characteristics of the patients. .posterior to the medial malleolus. The electrode atthis point was the anode. The cathode was placed Number of the patients (N) 28 Age (years), median (range) 66 (39^91)4 cm proximal to the anode. Analysis time was 50–100 Gender (N), F/M 15/13ms, gain was 10 mV, frequency bandwith was 0–2,000 Neurological findings, N (%)Hz. The N35 and P40 latencies were evaluated (Delisa Abnormal vibration or proprioception 15 (54) Abnormal pinprick sensation 6 (21)et al., 1994). Gait disturbance 9 (32) Loss of deep tendon reflexes 3 (10) Pyramidal tract finding 1 (3,6)Statistical analysis Mental impairment 1 (3,6) Hemoglobulin (g/dl), mean Æ SD 7.57 Æ 2.44 Statistical analysis was performed using SPSS WBC (ml), mean Æ SD 4,515 Æ 1,825software (SPSS, Inc.). Mann–Whitney U test was used Platelet (ml), mean Æ SD 123,892 Æ 79,017 MCV (fl), mean Æ SD 110.1 Æ23.9for comparing groups. Relationships between cate- Serum vitamin B12 (pg/ml), mean Æ SD 109.6 Æ 21.5gorical variables were compared using the chi-square Serum folate (ng/ml), mean Æ SD 7.98 Æ 4.11test. Coefficients of correlation (r) were calculated LDH (U/l), mean Æ SD 2,121 Æ2,295using the Spearman’s rank test. The level of signifi- LDH, lactate dehydrogenase; MCV, mean cell volume; WBC, whitecance in all statistical analysis was set at p , 0.05. blood cell. 249
  4. 4. Turgut et al. Journal of the Peripheral Nervous System 11:247–252 (2006)Table 2. The results of action potentials in patients with B12 deficiency who had normal conventional electrophysiological studiesand control subjects.* B12-deficient patients with normal conventional conduction studies (n ¼ 19) Control subjects (n ¼ 18)Nerves Latency (ms) Amplitude (mV) Velocity (m/s) Latency (ms) Amplitude (mV) Velocity (m/s)Median (s) 3.31 Æ 0.40 20.2 Æ 9.50 54.1 Æ 6.08 2.97 Æ 0.24 23.1 Æ7.71 53.5 Æ 4.27Ulnar (s) 2.82 Æ 0.31 18.8 Æ 8.89 53.5 Æ 4.27 2.46 Æ 0.22 22.8 Æ 7.92 63.9 Æ 5.85Tibial 4.22 Æ 0.83 9.31 Æ3.97 44.9 Æ 3.01 4.14 Æ 0.63 7.63 Æ 2.45 48.8 Æ 3.98Median (m) 3.52 Æ 0.43 7.86 Æ 2.64 53.7 Æ 3.61 3.32 Æ 0.37 7.53 Æ 2.14 59.1 Æ 4.54Ulnar (m) 2.60 Æ 0.33 9.78 Æ 2.04 66.2 Æ 5.37 2.27 Æ 0.22 9.38 Æ 2.28 70.6 Æ 7.16C. Peroneal 4.37 Æ 0.67 4.02 Æ 1.67 48.4 Æ 4.96 3.68 Æ 0.76 4.28 Æ 1.92 54.1 Æ 5.71Sural 2.89 Æ 0.81 13.3 Æ 5.71 49.2 Æ 7.66 2.68 Æ 0.63 12.4 Æ 4.39 55.9 Æ 12.7*The values are expressed as mean Æ SD.action potentials of sural nerve did not differ between patients had unsteady walking with positive Romberg’sthe same patients and the control subjects (Table 3). test, and SEP was abnormal (6 absent, 3 delayed) in all. Spasticity was evident in the lower limbs of aTibial SEPs patient with extensor plantar response. No motor deficit Tibial SEPs were abnormal in 20 (71%) of 28 was found in any of these patients.patients with delayed (14 patients) or absent (6 patients)responses. Nine patients were found to have neuro- Correlation analysispathy by conventional conduction studies, and they There was no difference between female andhad impaired tibial SEP simultaneously. Three patients male patients for all the electrophysiological studies.who had no SEP response had severe tibial nerve con- There was no correlation between all the electrophys-duction impairment, so impaired SEPs may be associ- iological findings and serum vitamin B12 and folateated with severe motor neuropathy, but they had the levels, hemoglobin level, mean cell volume, leuko-clinical finding of myelopathy. Two patients whose cyte and platelet counts, and lactate dehydrogenasedorsal sural SNAPs were absent had normal SEP level.responses and seven patients with abnormal SEPresponses had dorsal sural SNAPs. Tibial SEPs resultsare shown in Table 4. Six patients had stocking/glove type sensory loss, Discussionand all of them had sensory or sensorimotor polyneuro- There is a wide range of neurological disturbancespathy. Three patients with sensorimotor polyneuro- in patients with B12 deficiency including myelopathy,pathy had absent deep tendon reflexes. However, the peripheral neuropathy, altered mental status, andother three patients with polyneuropathy had no sen- optic neuropathy (Healton et al., 1991; Pandey et al.,sory loss and abnormality of deep tendon reflexes. 2004). It is difficult to distinguish findings due to theOf 20 patients with abnormal SEP responses, 15 involvement of the central nervous system fromhad abnormal vibration or proprioception, and nine those due to peripheral nervous system dysfunction (Roos, 1978; Healton et al., 1991; Shevell and Rosen- blatt, 1992), and there are no commonly acceptedTable 3. The results of sural and dorsal sural nerve action inclusion criteria in studies that investigated neurologi-potentials of patients whose dorsal nerve was recordable andthe comparison of these results with controls.* cal disturbances because there are no exact criteria for the diagnosis of B12 deficiency. For this reason, Patients Controls the frequency of peripheral neuropathy in vitamin B12Nerves (n ¼ 13) (n ¼ 18) p deficiency sharply differs among studies. This studyDorsal sural included B12-deficient patients with overt megaloblas- Amplitude (mV) 4.78 Æ 1.62 6.99 Æ 2.24 0.008 tic anemia; the cause of B12 deficiency was perni- Velocity (m/s) 34.5 Æ 6.22 46.8 Æ 11.2 0.001 Latency (ms) 3.89 Æ 0.70 3.09 Æ 0.59 0.003 cious anemia with high probability. We primarilySural investigated peripheral neuropathy in these patients Amplitude (mV) 14.1 Æ 5.68 12.4 Æ 4.39 0.70 by dorsal sural nerve conduction studies, in addition to Velocity (m/s) 50.3 Æ 8.33 55.9 Æ 12.7 0.17 conventional electrophysiological studies. Dorsal sural Latency (ms) 2.86 Æ 0.77 2.68 Æ 0.63 0.37 SNAPs were not recorded in 54% of the patients.*The values are expressed as mean Æ SD. Only 32% of patients were diagnosed as having 250
  5. 5. Turgut et al. Journal of the Peripheral Nervous System 11:247–252 (2006)Table 4. The results of tibial SEP studies.* No Delayed P40 N35 N50 response responseSEP right (n ¼ 28) 46.2 Æ 7.6 40.1 Æ7.27 54.4 Æ 6.32 6 patients 14 patientsSEP left (n ¼ 28) 47.1 Æ 8.09 40.0 Æ 7.25 58.7 Æ 11.4 6 patients 14 patientsSEP, sensory-evoked potential.*The values are expressed as mean Æ SD.polyneuropathy by conventional conduction studies. that 4 patients had isolated neuropathy on the basisFurthermore, when compared with normal in- of clinicoelectrophysiological profiles of 40 patients withdividuals, patients with recordable dorsal sural SNAPs B12 deficiency.had lower mean amplitude, slower mean velocity, There are a few studies proposing a correlationand longer mean latency. It was reported that there between clinicolaboratory findings and neurologicalwas high variability in dorsal sural SNAPs in normal in- findings in B12 deficiency. It has been reported thatdividuals, and standard cutoff values for dorsal sural the severity of neurological abnormalities increasesSNAPs for adults were not designated in the literature with increasing hematocrit levels (Healton et al.,(Killian and Foreman, 2001). For this reason, we did 1991; Savage and Lindenbaum, 1995). In anothernot use the quantitative values of the action poten- study, serum vitamin B12 level was found to correlatetials of dorsal sural nerve to diagnose peripheral well with sural SNAP and prolonged tibial SEP res-neuropathy. ponses (Puri et al., 2005). In spite of this, we did not Dorsal sural nerve conduction study is described find any correlation between electrophysiological find-as a new method providing an opportunity for the ings and clinicolaboratory findings. The studies thatevaluation of most distal nerves of lower extremities reported an inverse correlation between hematocritthat are usually first affected in peripheral neuropathy and the severity of neurologic findings included(Lee et al., 1992; Killian and Foreman, 2001). In dia- patients without anemia or mild anemia. Even in thebetic children, this method is reliable to show sub- study of Healton et al. (1991), this correlation wasclinical neuropathy (Turgut et al., 2004). Our results reported only in patients with normal hematocrit level.demonstrated that dorsal sural SNAP can aid to diag- Discordance between these studies and our studynose the peripheral neuropathy component of neuro- can be explained by the fact that we included onlylogical disturbances of B12 deficiency. patients with overt anemia. Exact reasons for the Myelopathic presentation has been reported to inverse correlation between hematocrit and thebe more common than peripheral neuropathy in B12 neurologic involvement are not known. Recently,deficiency (Misra et al., 2003). Furthermore, it is con- Carmel et al. (2003) showed significant differences introversial whether polyneuropathy may be present in homocysteine metabolism among patients with B12the absence of myelopathy (Saperstein et al., 2003). deficiency. They found that patients with B12 defi-In concordance with the literature, most of our pa- ciency who had neurologic defects had higher folate,tients presented with myelopathy. With clinical evalu- S-adenosylmethionine, cysteine, and cysteinylglycineations and SEP studies, we found that 71% of our levels than neurologically unaffected patients and thatpatients had posterior tract damage. Myelopathy low S-adenosylmethionine and glutathione levelspredominantly affects the posterior columns followed were independent predictors of anemia.by the anterolateral and anterior tracts (Hemmer As a result, with dorsal sural SNAP, most of theet al., 1998). We did not measure motor-evoked po- B12-deficient patients with megaloblastic anemia cantentials of our patients, but the presence of signs of be detected to have peripheral neuropathy. On thecentral motor pathway damage in only one patient on other hand, in concordance with previous studies,neurological examination made us think that damage dorsal tract involvement is more common thanto the pyramidal tract was not frequent in B12 defi- neuropathy in B12 deficiency.ciency as previously reported (Hemmer et al., 1998).Two patients with peripheral neuropathy diagnosedwith dorsal sural nerve conduction study did not havemyelopathy; this observation demonstrated that iso-lated neuropathy may be present in B12-deficient Referencespatients. Like our study, Misra et al. (2003) reported Carmel R (2003). Megaloblastic Anemias: Disorders ofthat 1 of 17 vegetarian patients with B12 deficiency had Impaired DNA synthesis. In: Wintrobe’s Clinical Hematol-isolated neuropathy, and Puri et al. (2005) also reported ogy, 11th Edn. Greer JP, Foerster J, Lukens JN, Rodgers 251
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