Correlation of nerve ultrasound,electrophysiological, and clinical findings in post Guillain‐Barré syndrome

We aimed to correlate functional disability, electrophysiology, and nerve ultrasound in patients after Guillain‐Barré syndrome (GBS). Seventy‐five healthy controls and 41 post‐GBS patients (mean 3.4 years, SD ± 2.91 years after onset) underwent clinical, sonographic, and electrophysiological evaluation. Compared to healthy controls, the post‐GBS patients showed: (1) a mean Rasch‐built Overall Disability Scale score of 31.8 (SD ± 11.6), modified Rasch‐built fatigue severity scale score of 15.6 (SD ± 3.2), Medical Research Council sum score of 22 (SD ± 5.6); (2) electrophysiological signs of permanent axonal loss in the majority of the peripheral nerves; (3) sonographical evidence of higher cross‐sectional area values (CSA) of the ulnar (elbow, p < 0.001), radial (spiral groove, p < 0.001), tibial nerve (popliteal fossa, p < 0.001) and brachial plexus (supraclavicular space, p < 0.001). No correlation between sonographic and electrophysiological findings was found. Neither nerve ultrasound nor electrophysiology correlated with muscle strength, overall disability, and fatigue scale. Compared to healthy controls, post‐GBS patients had significant functional disability. Despite significant abnormalities in both electrophysiology and ultrasound compared to healthy controls, neither electrophysiology nor nerve ultrasound correlated with functional disability of these patients.     

Multifocal motor neuropathy: correlation of nerve ultrasound,electrophysiological, and clinical findings

We present nerve ultrasound findings in multifocal motor neuropathy (MMN) and examine their correlation with electrophysiology and functional disability. Eighty healthy controls and 12 MMN patients underwent clinical, sonographic, and electrophysiological evaluation a mean of 3.5 years (standard deviation [SD] ± 2.1) after disease onset. Nerve ultrasound revealed significantly higher cross‐sectional area (CSA) values of the median (forearm, p < 0.001), ulnar (p < 0.001), and tibial nerve (ankle, p < 0.001) when compared with controls. Electroneurography documented signs of significantly lower values of the motor conduction velocity and compound muscle action potentials (cMAPs) in the upper arm nerves (median, ulnar, radial, p < 0.001). A significant correlation between sonographic and electrophysiological findings in the MMN group was found only between cMAP and CSA of the median nerve at the upper arm (r = 0.851, p < 0.001). Neither nerve sonography nor electrophysiology correlated with functional disability. MMN seems to show inhomogeneous CSA enlargement in various peripheral nerves, with weak correlation to electrophysiological findings. Neither nerve sonography nor electrophysiology correlated with functional disability. Multicentre, prospective studies are required to prove the applicability and diagnostic values of these findings.     

Motor nerve excitability after childhood Guillain‐Barré syndrome

Residual motor nerve dysfunction after pediatric Guillain‐Barré syndrome (GBS) was determined in an observational cross‐sectional cohort study in patients who previously developed GBS during childhood (<18 years). Ulnar motor nerve dysfunction was defined by compound motor action potential (CMAP) scan in patients after a follow up of at least 1 year compared with age‐matched healthy controls, in relation to clinical course and outcome. A total of 37 persons previously diagnosed with GBS in childhood were included with a mean age at current examination of 20.6 years (4–39 years). The median time between diagnosis and follow‐up was 11 years (range: 1–22 years). CMAP scanning indicated ulnar motor nerve dysfunction in 25 (68%) participants. The most frequent abnormality was a reduction in nerve excitability observed both in those with residual limb weakness and in the majority of those with complete recovery. CMAP scan characteristics were not related to prognostic factors or outcome. In conclusion, GBS in childhood results in residual motor nerve excitability disturbances, even in those completely recovered, probably reflecting altered physiology of regenerated peripheral nerves.     

Repair of the musculocutaneous nerve using the vagus nerve as donor by helicoid end‐to‐side technique: an experimental study in rats

Although several donor nerves can be chosen to repair avulsed brachial plexus nerve injury, available nerves are still limited. The purpose of this study is to validate whether the vagus nerve (VN) can be used as a donor. Eighteen Sprague‐Dawley male rats were divided into three groups (n = 6). The right musculocutaneous nerve (McN) was transected with differing subsequent repair. (1) HS‐VN group: a saphenous nerve (SN) graft‐end was helicoidally wrapped round the VN side (epi‐and perineurium was opened) with a 30 ° angle, distal SN end was coapted to the McN with end‐to‐end repair. (2) EE‐PN group: a SN was interpositionally grafted between the transected phrenic nerve (PN) and the McN by end‐to‐end coaptation. (3) Sham control group: McN was transected and not repaired and postoperative vital signs were checked daily. At three months, electrophysiology, tetanic force, wet biceps muscle weight, and histology were evaluated. Every tested mean value in HS‐VN group was significantly greater than the EE‐PN or the sham control groups (p < 0.05 or p < 0.005). The mean recovery ratio of regenerated nerve fibers was 96% and, in HS‐VN group, the mean recovery ratio of CMAP was 79%. No vital signs changed in any group. There was no statistical difference (p > 0.5) between the mean VN nerve‐fiber numbers of the segments proximal (2237 ± 134) and distal (2150 ± 156) to the VN graft‐attachment site. Histological analysis revealed no axon injury or intraneural scarring at any point along the VN. This study demonstrated that VN is a practical and reliable donor nerve for end‐to‐side nerve transfer. © 2017 Wiley Periodicals, Inc.     

Cdc42 GTPases facilitate TNF‐α‐mediated secretion of CCL2 from peripheral nerve microvascular endoneurial endothelial cells

Trafficking of autoreactive leukocytes across the blood‐nerve barrier and into peripheral nerves is an early pathological hallmark of Guillain‐Barré syndrome (GBS). Tumor necrosis factor‐α (TNF‐α), a proinflammatory cytokine, promotes transendothelial migration by upregulating endothelial expression of inflammatory mediators, including CCL2, a chemokine implicated in GBS. We sought to determine the mechanism by which TNF‐α induces expression and secretion of CCL2 from peripheral nerve microvascular endoneurial endothelial cells (PNMECs). Expression of CCL2 mRNA and protein in quiescent PNMEC cultures was minimal. In contrast, cultures treated with TNF‐α exhibited increased CCL2 mRNA and protein content, as well as protein secretion. Simvastatin significantly attenuated TNF‐α‐induced CCL2 secretion without affecting CCL2 mRNA or protein expression. Co‐incubation with geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate, prevented the effect of simvastatin. By comparison, inhibiting protein isoprenylation with GGTI‐298, but not FTI‐277, mimicked the effect of simvastatin and significantly attenuated transendothelial migration in vitro. Inhibition of the monomeric GTPase Cdc42, but not Rac1 or RhoA‐C, attenuated TNF‐α‐mediated CCL2 secretion. TNF‐α‐mediated trafficking of autoreactive leukocytes into peripheral nerves during GBS may proceed by a mechanism that involves Cdc42‐facilitated secretion of CCL2.     

Nerve ultrasound in miller fisher variant of Guillain–Barré syndrome

Introduction: Focal enlargement of the peripheral and spinal nerves, visualized using high‐resolution ultrasound (HRUS), has been reported in early Guillain–Barré syndrome, but not in the Miller Fisher variant. We report the use of HRUS in 2 patients who presented with acute ataxic neuropathy, areflexia, and ophthalmoparesis. Methods: Ultrasound and/or nerve conduction studies (NCS) of peripheral nerves, the vagus, and spinal nerves C5/6 were performed at onset and 2 weeks after immunoglobulin therapy. Results: Both patients fulfilled criteria for diagnosis of Miller Fisher syndrome (MFS). Laboratory findings revealed elevated ganglioside Q1b antibodies in both and an albuminolocytologic dissociation in 1 patient. In addition, 1 patient had NCS evidence for demyelinating neuropathy. However, ultrasound showed focal enlargement in the vagus, the spinal nerves, and/or in the peripheral nerves in both patients. After therapy, nerve enlargement decreased in parallel with clinical improvement. Conclusion: Spinal and/or peripheral nerve enlargement supports the diagnosis of MFS in early phases of the disease. Muscle Nerve 52 : 1106–1110, 2015     

Peripheral nerve size in normals and patients with polyneuropathy: An ultrasound study

Ultrasound has been used for visualizing peripheral nerve pathology. Our goal was to use ultrasound to quantitate the sizes of upper extremity nerves along their length in control subjects and patients with neuropathy. We measured median and ulnar nerve cross‐sectional areas (NCSA) in the arms of 190 subjects, including 100 with neuropathies and 90 controls. We found that NCSAs in healthy child and adult controls were greater with increasing height, at proximal sites, and at sites of entrapment. Nerves were enlarged in all Charcot–Marie–Tooth 1A (CMT‐1A) (11 of 11; 100%), most chronic inflammatory demyelinating polyneuropathy (CIDP) (31 of 36; 86%), half of Guillain–Barré syndrome (GBS) (8 of 17; 47%), but few axonal neuropathy (7 of 36, 19%) subjects. In GBS, nerve enlargement occurred early and with minimal electrodiagnostic abnormalities in some patients. We conclude that NCSA measured by ultrasound is a quantifiable marker of nerve features that should be corrected for patient characteristics and nerve site. NCSA is generally larger in demyelinating than it is in axonal polyneuropathies. Muscle Nerve, 2009     

High mortality from Guillain‐Barré syndrome in Bangladesh

Although Guillain‐Barré syndrome (GBS) has higher incidence and poor outcome in Bangladesh, mortality from GBS in Bangladesh has never been explored before. We sought to explore the frequency, timing, and risk factors for deaths from GBS in Bangladesh. We conducted a prospective study on 407 GBS patients who were admitted to Dhaka Medical College Hospital, Dhaka, Bangladesh from 2010 to 2013. We compared deceased and alive patients to identify risk factors. Cox regression model was used to adjust for confounders. Of the 407 GBS patients, 50 (12%) died, with the median time interval between the onset of weakness and death of 18 days. Among the fatal cases, 24 (48%) were ≥40 years, 36 (72%) had a Medical Research Council sum score ≤20 at entry, 33 (66%) had a progressive phase <8 days, and 27 (54%) required ventilation support. Ten patients (20%) died due to unavailability of ventilator. The strongest risk factor for deaths was lack of ventilator support when it was required (HR: 11.9; 95% confidence interval [CI]: 4.6–30.7). Other risk factors for death included age ≥40 years (HR: 5.9; 95% CI: 2.1–16.7), mechanical ventilation (HR: 2.3; 95% CI: 1.02–5.2), longer progressive phase (>8 days) (HR: 2.06; 95% CI: 1.1–3.8), autonomic dysfunction (HR: 1.9; 95% CI: 1.05–3.6), and bulbar nerve involvement (HR: 5.4; 95% CI: 1.5–19.2). In Bangladesh, GBS is associated with higher mortality rates, which is related to lack of ventilator support, disease severity, longer progressive phase of the disease, autonomic dysfunction, and involvement of the bulbar nerves.     

Diabetes mellitus may affect short‐term outcome of Guillain‐Barré syndrome

We sought to determine influence of diabetes mellitus on Guillain‐Barré syndrome (GBS) course and short‐term prognosis. Among the 257 GBS patients included in this retrospective study, diabetes mellitus was present in 17%. The degree of disability at admission and on discharge was assessed according to the GBS Disability Scale (mild disability = 0–3, severe disability = 4–6). Even after correction for age, diabetes mellitus was significantly associated with more severe disability at nadir (odds ratio, OR = 3.4, p < 0.05) and on discharge (OR = 2.0, p < 0.05). Linear regression analysis with multiple factors included showed that age and presence of diabetes were significant predictors of severe disability at nadir (adjusted R² = 0.21, p < 0.05), and on discharge (adjusted R² = 0.19, p < 0.05). The presence of diabetes mellitus affects short‐term prognosis of GBS, independent of age.     

Diagnostic nerve ultrasound in Charcot–Marie–Tooth disease type 1B

Ultrasound is emerging as a useful tool for evaluation of neuromuscular conditions, because it can provide high‐resolution anatomic information to complement electrodiagnostic data. There have been few studies in which ultrasound was used to assess the peripheral nerves of individuals with Charcot–Marie–Tooth (CMT) disease and none involving CMT type 1B. In this study we compared nerve cross‐sectional area in individuals from a single large family with CMT 1B with normal, healthy controls. We also assessed for cranial nerve enlargement in those with CMT 1B with cranial neuropathies compared to those with CMT 1B without cranial neuropathies. Individuals with CMT 1B have significantly larger median and vagus nerves than healthy controls, but no difference was seen in cranial nerve size between those with versus those without cranial neuropathies. This is the first study to characterize the ultrasonographic findings in the peripheral nerves of individuals with CMT 1B. Muscle Nerve 40: 98–102, 2009     

Anatomical study of the iliohypogastric,ilioinguinal, and genitofemoral nerves using high‐resolution ultrasound

Introduction: In this study we aimed to determine whether high‐resolution ultrasound (US) can identify the iliohypogastric (IH), ilioinguinal (II), and genitofemoral (GF) nerves and their relations. Methods: This investigation, initially undertaken in cadavers, was followed by a high‐resolution US study in 30 healthy adult volunteers (180 nerves) by 2 musculoskeletal radiologists on separate occasions, using 2 different approaches (proximal to distal and distal to proximal). A 0–3 scale was used to assess nerve visibility. Location and course of the IH, II, and GF nerves and their relations to adjacent anatomical structures were analyzed. Results: Nerves and their terminal branches were better visualized with the distal‐to‐proximal approach (P < 0.05). Visualization of the terminal branches was possible in up to 60% of volunteers. Conclusions: High‐resolution ultrasound (US) can identify the IH, II, and GF nerves at the level of the abdominal wall and the terminal branches in the majority of volunteers. Muscle Nerve 51 : 42–48, 2015     

Transcutaneous cervical vagal nerve stimulation modulates cardiac vagal tone and tumor necrosis factor‐alpha

The vagus nerve is a central component of cholinergic anti‐inflammatory pathways. We sought to evaluate the effect of bilateral transcutaneous cervical vagal nerve stimulation (t‐VNS) on validated parameters of autonomic tone and cytokines in 20 healthy subjects. 24 hours after t‐VNS, there was an increase in cardiac vagal tone and a reduction in tumor necrosis factor‐α in comparison to baseline. No change was seen in blood pressure, cardiac sympathetic index or other cytokines. These preliminary data suggest that t‐VNS exerts an autonomic and a subtle antitumor necrosis factor‐α effect, which warrants further evaluation in larger controlled studies.     

Measurement of motor root conduction time at the early stage of Guillain–Barre syndrome

Background and purpose: As they are mainly performed at distal nerve parts, routine electrophysiological examinations can fail to detect the abnormalities at the early stage of Guillain–Barre syndrome (GBS) because of predominant involvement of proximal nerve segments. Measurements focused on proximal conduction can provide additional findings. We investigated the diagnostic significance of motor root conduction time (MRCT) at the early stage of GBS. Methods: Study was performed in 30 healthy volunteers and within the first week of 12 patients with GBS. MRCT was calculated as the latency differences between motor nerve conduction time (MNCT) obtained by cervical magnetic stimulation and total peripheral motor conduction time obtained by electrical stimulation of ulnar nerve. Also MNCT/MRCT ratio was calculated in each subject. Results: There were statistically significant differences between groups for MRCT (P < 0.0001) and MNCT/MRCT ratio (P < 0.0001). Although the F‐wave latency at ulnar nerve was abnormal only in 33%, MRCT was significantly prolonged in 83% of patients. In three patients, prolongation of MRCT was the only abnormality at the first electrodiagnostic examination. Conclusions: Motor root conduction time as a non‐invasive method can provide additional and confirmative information at the early stage of GBS in which routine nerve conduction studies may fail to detect the focal demyelination.     

Proximal nerve lesions in early Guillain–Barré syndrome: implications for pathogenesis and disease classification

Guillain–Barré syndrome (GBS) is an acute-onset, immune-mediated disorder of the peripheral nervous system. In early GBS, arbitrarily established up to 10 days of disease onset, patients could exhibit selective manifestations due to involvement of the proximal nerves, including nerve roots, spinal nerves and plexuses. Such manifestations are proximal weakness, inaugural nerve trunk pain, and atypical electrophysiological patterns, which may lead to delayed diagnosis. The aim of this paper was to analyze the nosology of early GBS reviewing electrophysiological, autopsy and imaging studies, both in acute inflammatory demyelinating polyneuropathy (AIDP) and acute motor/motor-sensory axonal neuropathy (AMAN/AMSAN). Early electrophysiology showed either well-defined demyelinating or axonal patterns, or a non-diagnostic pattern with abnormal late responses; there may be attenuated M responses upon lumbar root stimulation as the only finding. Pathological changes predominated in proximal nerves, in some studies, most prominent at the sides where the spinal roots unite to form the spinal nerves; on very early GBS endoneurial inflammatory edema was the outstanding feature. In the far majority of cases, spinal magnetic resonance imaging showed contrast enhancement of cauda equina, selectively involving anterior roots in AMAN. Both in AIDP and AMAN/AMSAN, ultrasonography has demonstrated frequent enlargement of ventral rami of C5–C7 nerves with blurred boundaries, whereas sonograms of upper and lower extremity peripheral nerves exhibited variable and less frequent abnormalities. We provide new insights into the pathogenesis and classification of early GBS.     

Guillain‐Barré syndrome: subtypes and predictors of outcome from India

There is a paucity of large studies evaluating the subtypes of Guillain‐Barré syndrome (GBS) and their outcome from Southeast Asia. We report cliniconeurophysiological subtypes of GBS and their correlation with triggering events and 3‐month outcome from northern India. Three hundred and twenty eight consecutive patients with GBS were clinically evaluated, including their triggers, severity, autonomic involvement, cranial nerve palsy, and respiratory paralysis. Nerve conduction study (NCS) was repeated at 3 weeks if the initial study was normal. They were categorized into acute inflammatory demyelinating polyradiculoneuropathy (AIDP), acute motor axonal neuropathy (AMAN), acute motor sensory axonal neuropathy (AMSAN), inexcitable motor nerve, and equivocal. Clinically, 204 (62.2%) patients had pure motor, 106 (32.3%) motor sensory, 16 (4.9%) Miller Fisher syndrome, and 2 (0.6%) pure sensory GBS. Based on NCS, 242 (73.8%) had AIDP, 44 (13.4%) AMAN, 15 (4.6%) AMSAN, 8 (2.4%) inexcitable motor nerves, and 27 (8.2%) equivocal GBS. AIDP patients were older, more common in summer, had lesser peak disability, and better outcome compared to those with AMAN. Eleven (3.4%) patients died and 48 (14.6%) had poor outcome at 3 months. The poor outcome was related to severity, dysautonomia, and inexcitable motor nerves. AIDP is the commonest variant of GBS in our study and has better outcome compared to AMAN.     

Disruption of nodal architecture in skin biopsies of patients with demyelinating neuropathies

Cutaneous nerves represent the most distal part of the sensory nervous system. We took advantage of the good discernibility of longitudinal myelinated fibers in skin biopsies to analyze the distribution of nodal and paranodal proteins in neuropathies and to assess nodal disorganization as a diagnostic marker of demyelinating neuropathy (NP). We analyzed myelinated nerve fibers in skin biopsies from the finger and the proximal leg of 52 prospectively recruited patients with different peripheral neuropathies and 17 controls. We performed immunohistochemical double labeling with anti‐MBP, anti‐PGP9.5, anti‐caspr, anti‐pan‐neurofascin, and anti‐pan‐sodium‐channel. Three potential features of demyelinating NP could be established: elongated nodes of Ranvier and dispersion of contactin‐associated protein (caspr) staining were found more often in demyelinating than in axonal neuropathies (p < 0.05) and were not detectable in normal controls. Broadening of neurofascin staining was detectable more often in demyelinating neuropathies compared with normal controls (p < 0.05). Our data suggest that pathological changes of nodal architecture can be visualized in skin biopsies and that the detection of elongated nodes of Ranvier and alterations in the distribution of paranodal proteins may be useful in the diagnostic assessment of peripheral NP.     

Sonographic evaluation of the sciatic nerve in patients with lower‐limb amputations

Hypertrophy of the sciatic nerve after lower‐limb amputation in patients with sarcomas has been previously reported by magnetic resonance imaging; however, sonographic evaluation of the sciatic nerve after lower‐limb amputation due to nonmalignant causes has not been done before. Therefore, the aim of this study was to perform imaging of the sciatic nerve in lower‐limb amputees and to find out whether sonographic findings were related to clinical characteristics. Twenty‐three males with lower‐limb amputations due to traumatic injuries were enrolled. Sonographic evaluations were performed using a linear array probe (Aloka UST‐5524‐7.5 MHZ ). Sciatic nerve diameters were measured bilaterally at the same level, and the values of the normal limbs were taken as controls. Sciatic nerve width and thickness values were found to be greater on the amputated sides than the normal sides (P = 0.001). The thickness values were greater in above‐knee amputees than below‐knee amputees (P = 0.05). Subjects with a neuroma also had thicker sciatic nerves (P = 0.04). The diameters were found not to change between subjects with different liners (P > 0.05), but they were correlated with time after amputation (r = 0.6, P = 0.006; r = 0.4, P = 0.05, respectively). Our results clearly show that the sciatic nerves were wider and thicker on the amputated sides. Amputation level, duration, and the presence of a neuroma seem to affect the eventual diameters of the nerves. Muscle Nerve, 2010     

Novel anti‐idiotype antibody therapy for lipooligosaccharide‐induced experimental autoimmune neuritis: Use relevant to Guillain‐Barré syndrome

Campylobacteriosis is a frequent antecedent event in Guillain‐Barré syndrome (GBS), inducing high‐titer serum antibodies for ganglioside antigens in the peripheral nervous system (PNS). Molecular mimicry between the lipooligosaccharide (LOS) component of Campylobacter jejuni and human peripheral nerve gangliosides is believed to play an important role in the pathogenesis of GBS. Conventional treatment strategies for patients with GBS include plasmapheresis, intravenous immunoglobulin (IVIG), and immunosuppression, which are invasive or relatively ineffective. In this study, we used our animal model of GBS, in which Lewis rats were immunized with GD3‐like LOS isolated from C.jejuni. The animals developed anti‐GD3 ganglioside antibodies and manifested neuromuscular dysfunction. To develop novel therapeutic strategies, we treated the animals by intraperitoneal administration of an anti‐GD3 antiidiotype monoclonal antibody (BEC2) that specifically interacts with the pathogenic antibody. The treated animals had a remarkable reduction of anti‐GD3 antibody titers and improvement of motor nerve functions. The results suggest that ganglioside mimics, such as antiidiotype antibodies, may be powerful reagents for therapeutic intervention in GBS by neutralizing specific pathogenic antiganglioside antibodies. © 2010 Wiley‐Liss, Inc.     

Guillain‐Barré syndrome in the elderly

The aim of the study was to analyze specific features of Guillain‐Barré syndrome (GBS) in old people. The study included 403 GBS patients (62% young [<60 years], 35% young‐old [60–80 years], and 3% old‐old [>80 years]). Diagnosis of GBS was made according to the National Institute of Neurological Disorders and Stroke (NINDS criteria). Severe disability (GBS disability score of >3) at nadir was more common in old compared with young patients (p = 0.0001) as was mortality (9% vs. 2%, respectively). Acute motor and sensory axonal neuropathy and hyponatremia were more common in old compared with young patients (12% vs. 6% and 27% vs. 18%, respectively, p = 0.04). A positive history for malignancy was more than three times more common in old than young patients (11% vs. 3%, respectively, p = 0.01). Disability on nadir was similar in young‐old and old‐old subjects with disability on discharge being more severe in old‐old (p = 0.04) suggesting slower recovery in this subgroup. Bulbar symptoms were more common in old‐old compared with young‐old (50% vs. 19%, respectively, p = 0.01). Comorbidities were present in virtually all old‐old patients compared with 66% of young‐old patients (p = 0.04). In conclusion, Elderly patients, and especially old‐old patients, with GBS have more severe disease with slower recovery than do younger patients.     

The ventral caudal nerve: a physiologic‐morphometric study in three different rat strains

The caudal nerve is often used for investigating alterations in nerve conduction velocity (NCV) to determine the presence of peripheral neuropathy in animal models. In the present study, the rat caudal nerve of two outbred strains (Wistar Hannover and Sprague‐Dawley) and one inbred strain (Fischer‐344) was analyzed with regard to morphologic, morphometric, and physiologic features. In all three strains, we calculated the myelinated fiber diameter, myelinated axon diameter, and g‐ratio in the proximal caudal nerve and correlated these results with NCV in the distal caudal nerve. Although the caudal nerves were morphologically similar in the three rat strains, a significant difference was present morphometrically: there was a statistically significant increase in the g‐ratio associated with a reduction in myelinated fiber diameter in Fischer‐344 rats vs. Wistar Hannover and Sprague‐Dawley animals (p < 0.01). However, there was no significant difference in NCV results in the distal caudal nerve. The present study adds morphologic and morphometric information on the rat caudal nerve that might be useful for a better interpretation of studies involving this nerve and its pathological changes in experimental models of peripheral neuropathies.