Flecainide reverses neuropathic pain and suppresses ectopic nerve discharge in rats

We investigated effects of flecainide, a Class IC sodium channel blocker, in the rat chronic constrictive injury (CCI) and ectopic nerve discharge models. In the behavioral evaluation, 2, 6, and 12 mg/kg flecainide were intravenously given to the CCI model, and a dose-dependent analgesic effect was shown on both thermal hyperalgesia and tactile allodynia. In the electrophysiological evaluation using the ectopic nerve discharge model produced by saphenous neurectomy, i.v. administration of 2, 6, and 12 mg/kg flecainide suppressed spontaneous discharge at the peripheral nerve level in a dose-dependent fashion as with the behavioral evaluation, but flecainide did not affect nerve conduction at the dose of 12 mg/kg.

Quadriceps muscle weakness following acute hemiplegic stroke

OBJECTIVE

To determine whether quadriceps muscle weakness develops on the side ipsilateral to the brain lesion in the first week following acute ischaemic hemiplegic stroke.

DESIGN

A prospective study of muscle strength.

SETTING

Acute stroke unit (ASU) in a teaching hospital.

SUBJECTS

Ten patients admitted within 48 hours of stroke onset, and 10 healthy age-matched controls.

INTERVENTIONS

Repeat nonvolitional measurements of quadriceps muscle strength of the unaffected limb in patients and the right leg in normal subjects using magnetic femoral nerve stimulation (MS), prospectively one week apart. In addition the level of voluntary activation was assessed during a maximum voluntary contraction (MVC) manoeuvre. The Trunk Control Test (TCT) was measured in the patients.

RESULTS

The median (95% confidence interval, (CI)) baseline quadriceps twitch tension (Tw Q) and MVC in the control group were 9.4 kg (6.1-12.5 kg) and 37.2 kg (23.8-54.6 kg), and in the stroke group were 7.6 kg (4.4-9.9 kg) and 12.15 kg (7.9-30.8 kg). The median (95% CI) change in Tw Q and MVC respectively between baseline and one week later were 1.75% (-9.8 to 8%) and 5.45% (-15.1 to 22.7%) (NS) in the control group and -16.2% (-6 to -25.9%) and -30.45% (0 to -78.6%) (p < 0.01) in the stroke patients. There was a significant correlation between the percentage fall in Tw Q and both change in TCT (rs = 0.83, p < 0.01) and percentage change in body weight (rs = 0.83, p < 0.01).

CONCLUSION

In the first week after acute hemiplegic stroke, weakness develops in the unaffected leg.

Modulation of presynaptic inhibition and disynaptic reciprocal Ia inhibition during voluntary movement in spasticity

The aim of the study was to investigate whether impaired control of transmission in spinal inhibitory pathways contributes to the functional disability of patients with spasticity. To this end, transmission in the pathways mediating disynaptic reciprocal Ia inhibition and presynaptic inhibition was investigated in 23 healthy subjects and 20 patients with spastic multiple sclerosis during ankle dorsiflexion and plantar flexion. In healthy subjects, but not in spastic patients, the soleus H reflex was depressed at the onset of dorsiflexion (300 ms rise time, 20% of maximal voluntary effort). At the onset of plantar flexion, the soleus H reflex was more facilitated in the healthy subjects than in the patients. The H reflex increased more with increasing level of tonic plantar flexion and decreased more with dorsiflexion in the healthy subjects than in the spastic patients. Transmission in the disynaptic Ia reciprocal inhibitory pathway from ankle dorsiflexors to plantar flexors was investigated by conditioning the soleus H reflex by previous stimulation of the common peroneal nerve (conditioning-test interval 2-3 ms; stimulation intensity 1.05 times the motor response threshold). At the onset of dorsiflexion, stimulation of the common peroneal nerve evoked a significantly larger inhibition than at rest in the healthy subjects but not in the spastic patients. At the onset of plantar flexion the inhibition decreased in the healthy subjects, but because only weak inhibition was observed at rest in the patients it was not possible to determine whether a similar decrease occurred in this group. There were no differences in the modulation of inhibition during tonic plantar flexion and dorsiflexion in the two populations. Presynaptic inhibition of Ia afferents terminating on soleus motor neurones was evaluated from the monosynaptic Ia facilitation of the soleus H reflex evoked by femoral nerve stimulation. Femoral nerve facilitation was decreased at the onset of dorsiflexion and increased at the onset of plantar flexion in the healthy subjects and patients, but the changes were significantly greater in the healthy subjects. There was no difference between the two populations in the modulation of presynaptic inhibition during tonic plantar flexion and dorsiflexion. It is suggested that the abnormal regulation of disynaptic reciprocal inhibition and presynaptic inhibition in patients with spasticity is responsible for the abnormal modulation of stretch reflexes in relation to voluntary movement in these patients. Lack of an increase in reciprocal inhibition and presynaptic inhibition at the onset of dorsiflexion may be responsible for the tendency to elicitation of unwanted stretch reflex activity and co-contraction of antagonistic muscles in patients with spasticity.

The crossed femoral nerve stretch test to improve diagnostic sensitivity for the high lumbar radiculopathy: 2 case reports

The femoral nerve stretch test (FNST) is commonly used to assess high lumbar radiculopathy. It may be falsely positive secondary to tight or injured muscles of the anterior thigh, and to osseous or joint pathology in and about the hip. We report on the crossed FNST, which may improve the specificity of the FNST. Two cases that occurred within 2 months are presented. The physical examinations suggested high lumbar radiculopathy, which was confirmed by both the FNST and crossed FNST. The crossed FNST may thus be a valuable screening test that further supports a diagnosis of upper lumbar radiculopathy. Further study is necessary to identify its prevalence in the assessment of the high lumbar radiculopathy.

Sensory disturbance of the thigh after renal transplantation

PURPOSE

Although sensory disturbance of the anterior and/or lateral thigh often develops after renal transplantation, this complication is overlooked because of the minor degree of disability. We evaluated the rate of sensory disturbance of the thigh after renal transplantation.

MATERIALS AND METHODS

We examined neurological deficits of the thigh on the operated side in 61 patients who underwent renal transplantation, including 48 using the internal and 13 using the external iliac artery.

RESULTS

We noted sensory disturbance in 23 of the 61 cases, including 20 of the 48 in which the internal iliac artery was used. One patient had complete femoral nerve palsy involving motor weakness. Sensory disturbance was in the anterior thigh in 15 patients, in the lateral thigh in 3, and on the anterior and lateral thigh in 2. Postoperatively there was sensory disturbance of the thigh in 3 of the 13 patients in whom the external iliac artery was used. Sensory disturbance persists in all 3 cases at the time of this report, including in the anterior thigh in 1, and in the anterior and lateral thigh in 2.

CONCLUSIONS

The rate of sensory disturbance of the thigh after renal transplantation is high. Therefore, we should inform patients of the possibility of sensory disturbance before renal transplantation surgery is performed.

Effect of thigh flexion on somatosensory evoked potentials in meralgia paresthetica

Standing with the thigh extended or lying still provokes and stepping or sitting relieves the symptoms in some patients with meralgia paresthetica. We performed this study to confirm this clinical feature with electrophysiological measures. Twenty-one symptomatic and 17 asymptomatic legs of 19 patients were evaluated by somatosensory evoked potential studies in both extended and flexed thigh positions. In the symptomatic group, thigh flexion significantly reduced the cortical latency. This finding is parallel with the relief of the symptoms.

Postoperative lateral femoral cutaneous neuropathy

Lateral femoral cutaneous (LFC) neuropathy was diagnosed in a woman who developed pain and paresthesias in the right thigh 6 days after abdominal hysterectomy by a suprapubic approach. After surgery, the patient slept in the fetal position to control the postoperative suprapubic pain. The LFC neuropathy improved with therapy including avoidance of hip flexion during sleep. Prolonged postoperative hip flexion to relieve the abdominal incisional pain provides an explanation for LFC neuropathy after abdominal surgery when the onset of symptoms is delayed.

Motor neuropathy in porphobilinogen deaminase-deficient mice imitates the peripheral neuropathy of human acute porphyria

Acute porphyrias are inherited disorders caused by partial deficiency of specific heme biosynthesis enzymes. Clinically, porphyrias are manifested by a neuropsychiatric syndrome that includes peripheral neuropathy. Although much is known about the porphyrias' enzyme defects and their biochemical consequences, the cause of the neurological manifestations remains unresolved. We have studied porphyric neuropathy in mice with a partial deficiency of porphobilinogen deaminase (PBGD). PBGD-deficient mice (PBGD-/-) imitate acute porphyria through massive induction of hepatic delta-aminolevulinic acid synthase by drugs such as phenobarbital. Here we show that PBGD-/- mice develop impairment of motor coordination and muscle weakness. Histologically femoral nerves of PBGD-/- mice exhibit a marked decrease in large-caliber (>8 microm) axons and ultrastructural changes consistent with primary motor axon degeneration, secondary Schwann cell reactions, and axonal regeneration. These findings resemble those found in studies of affected nerves of patients with acute porphyria and thus provide strong evidence that PBGD deficiency causes degeneration of motor axons without signs of primary demyelination, thereby resolving a long-standing controversy. Interestingly, the neuropathy in PBGD-/- mice developed chronically and progressively and in the presence of normal or only slightly (twofold) increased plasma and urinary levels of the putative neurotoxic heme precursor delta-aminolevulinic acid. These data suggest that heme deficiency and consequent dysfunction of hemeproteins can cause porphyric neuropathy.

Meralgia paresthetica secondary to limb length discrepancy: case report

Meralgia paresthetica consists of pain and dysthesia in the lateral thigh caused by entrapment of the lateral femoral cutaneous nerve (L2-L3) underneath the inguinal ligament. Abdominal distension, tight clothing, and hip hyperextension are all described causes of this condition. To our knowledge this has never been attributed to a limb length discrepancy. We present a 51-year-old man with a long-standing history of right sided meralgia paresthetica. History and physical and radiological examination were unrewarding except that his left leg was shorter than the right by 2 cm. Nerve conduction studies of the lateral femoral cutaneous nerve on the left had a normal latency and amplitude but were absent on the right. To prove the hpothesis that the limb length discrepancy was responsible for the condition, a single subject study was performed. The presence or absence of pain and dysesthesia in the right thigh was the observed behavior. Intervention consisted of wearing a 1.5-cm lift in the left or right shoe for 2 weeks each with an intervening 2-week lift-free period. Pain was recorded on a numeric scale and numbness as being present or absent. There was continuing pain without and with the lift in the right shoe but no pain or numbness with the lift in left shoe. It was concluded that the limb length discrepancy was responsible for the meralgia paresthetica. Pertinent literature and possible pathomechanics are discussed.

Electrophysiological features in the management of meralgia paraesthetica

Meralgia paraesthetica is a condition which presents with pain and paresthesia over the anterolateral thigh, due to entrapment of the lateral femoral cutaneous nerve. Our local experience of 12 cases highlights the usefulness of antidromic sensory nerve conductions in the diagnostic and prognostic aspects of this condition. Follow-up studies suggest that patients with initial reduction rather than absent sensory amplitudes on the affected side more likely to experience symptomatic improvement over an 8 to 24 month period.

Mononeuropathy multiplex in hemophilia: an electrophysiologic assessment

Single nerve lesion or mononeuropathy caused by extrinsic compression of hematoma or hemarthrosis is consistently reported for hemophilic patients. To study the manifestation of peripheral nerve lesions, an extensive nerve conduction study of peripheral nerves and specific nerves in correlation with clinical involvement was carried out on 126 hemophilic patients. We found 24 patients with 34 peripheral nerve lesions. The frequency of nerve lesion positively correlated with the severity of hemophilia (p < 0.01) and increasing age (p < 0.05). Nerve lesions occurred more commonly in lower extremities than in upper extremities. The femoral nerve was most commonly involved. Seven patients were identified to have mononeuropathy multiplex with 2 or more nerve lesions involving more than one extremity. All of these patients had chronic condition. Our findings suggest that mononeuropathy multiplex may occur in hemophilic patients.

Healing of tibial fractures is not impaired after acute hindlimb ischemia in rats

The influence of transient circulatory arrest on the healing of closed tibial fractures was investigated in rats by the use of a hindlimb tourniquet technique. Twenty-four animals were randomly divided into three groups. In all animals, the left lower leg was fractured and fixed with an intramedullary nail system. In the ischemic group, complete acute transient ischemia for 4.5 h and neurapraxia of the sciatic and femoral nerves were induced prior to fracture. In the neurapraxia group, the sciatic and femoral nerves were crushed with forceps before fracture. In the control group, no other intervention than fracture was made. The rats of the control group ambulated normally 3-4 days after the operation. The animals of the ischemic and neurapraxia groups resumed normal weight-bearing after about 3 weeks. After 6 weeks, all animals were killed, and mechanical strength and bone mineral turnover of the healing tibia as well as blood flow of the bone and musculature were evaluated. The weight of the tibia and the corresponding anterior tibial muscle in the ischemic and neurapraxia animals were reduced compared with the control rats. Bone mineral turnover was found to be lower in the ischemic group. There were no differences between the groups in mechanical strength nor in blood circulation of bone and muscle. In conclusion, complete, acute hindlimb ischemia for 4.5 h in rats did not cause delayed healing of closed tibial fractures.

[Lateral femoral cutaneous neuropathy: paresthetic meralgia. Neurophysiological diagnosis]

INTRODUCTION

The neurophysiological approach to meralgia paresthetica (MP) deals with the possible abnormalities demonstrated in the peripheral nerve conduction and/or somatosensory evoked potentials (SEP) of the lateral femoral cutaneous nerve (LFCN).

MATERIAL AND METHODS

To ascertain the diagnostic value of these methods, a group of 23 patients with unilateral MP symptoms has been studied; SEP of LFCN was also evaluated in a series of normal people.

RESULTS

LFCN conduction was abnormal on the symptomatic side in 47.6% of the cases and nerve potential was absent on both sides in all the rest. SEPLFCN showed some impairment in 91% of the cases on the symptomatic side and responses were obtained on the asymptomatic side in every case; the most common abnormality was the delay of the response followed by its followed by its absence. In the normal group, the amplitude of potentials registered on the contralateral scalp to the stimulated side was usually higher than that registered on the median line, where they eventually lacked. Methodologically, this fact supports the need of a multiple recording of the SEPLFCN on the scalp.

CONCLUSIONS

The SEPLFCN should be considered as the main technique for the objective diagnosis of MP and although LFCN conduction can supply useful information in individual cases, its exclusive use may lead to rather many positive false results.

Far lateral lumbar disc herniation. The key to the intertransverse approach

Of a total of 330 patients requiring operation on a lumbar disc, 20 (6.1%) with lateral disc prolapse had a new muscle-splitting, intertransverse approach which requires minimal resection of bone. There were 16 men and 4 women with a mean age of 52 years. All had intense radicular pain, 15 had femoral radiculopathy and 19 a neurological deficit. Far lateral herniation of the disc had been confirmed by MRI. At operation, excellent access was obtained to the spinal nerve, dorsal root ganglion and the disc prolapse. The posterior primary ramus was useful in locating the spinal nerve and dorsal root ganglion during dissection of the intertransverse space. At review from six months to four years, 12 patients had excellent results with no residual pain and six had good results with mild discomfort and no functional impairment. Two had poor results. There had been neurological improvement in 17 of the 20 patients. We report a cadaver study of the anatomy of the posterior primary ramus. It is readily identifiable through this approach and can be traced down to the spinal nerve in the intertransverse space. We recommend the use of a muscle-splitting intertransverse approach to far lateral herniation of the disc, using the posterior primary ramus as the key to safe dissection.

[Paralysis of the crural nerve as immediate complication of abdominal hysterectomy. Report of 14 cases]

We report 14 cases of Femoral nerve palsy following abdominal hysterectomy like complication; we found predisponents factors were: Lower weight in relation to ideal weight and structure in 100% of cases, this point shows to be significative. Other involucrated factors were Pfannenstiel incition on thin patients; The Sullivan O'connor's retractors was considered the unchain factor, because the valves are long in relation to thinness patients.

Surgical correction of proximal femoral nerve entrapment

BACKGROUND

Femoral nerve palsy is usually a result of trauma. Isolated femoral nerve palsy without external trauma is restricted to occasional case reports in various circumstances.

CASE DESCRIPTION

Three cases of nontraumatic femoral nerve palsy are reported who presented with pain and weakness. Symptoms were relieved by transection of the iliopectineal arch. This is believed to be a newly described syndrome. An additional case of femoral nerve entrapment following vaginal hysterectomy is described. This case presented only as a pain syndrome.

CONCLUSIONS

There is a syndrome of femoral nerve entrapment at the iliopectineal arch that can be easily relieved by sectioning of this arch, analogous to carpal tunnel syndrome. Several cases of femoral nerve palsy previously reported may be examples of this syndrome.

Motor and sensory specificity of host nerve axons influence nerve allograft rejection

Previous studies have shown both survival and loss of regenerated host axons within nerve allograft segments after withdrawal of Cyclosporin A (CsA) immunosuppression. We hypothesized that the nature of end-organ reinnervation may influence the response of the axon, with survival of axons for appropriate innervation vs degeneration for inappropriate innervation. The rat femoral nerve model was chosen, as it has approximately equal sensory (S) and motor (M) divisions. Four ACI rat peroneal nerve allografts were sutured in straight (right leg: MM and SS) or switched (left leg; MS and SM) orientation in each femoral nerve transection gap in each Lewis rat recipient. Rats received CsA for 8 weeks to allow end-organ reinnervation, after which immunosuppression was discontinued. Rats were killed at various times thereafter, and underwent histologic and morphometric analysis of the graft segment axons. The regenerated axon population in the allograft reflected the nerve of origin: significantly more but smaller fibers when the proximal nerve was sensory and fewer but larger fibers when the proximal nerve was motor. After CsA withdrawal, there was a marked decrease of host axons as part of an ensuing rejection episode. The overall proportional decrease of axons was similar across all nerve orientation groups and, therefore, did not appear to be influenced by the nerve of origin or by the end-organ. However, the sensory proximal groups (SS and SM) contained more mature, noninjured fibers, while the motor proximal groups (MM and MS) contained significantly more degeneration and newly regenerating axons. We conclude that the motor or sensory nerve origin of the host axon, rather than the end-organ, influences axon survival after immunosuppression cessation. It is hypothesized that sensory axons may be more resilient while motor axons are selectively vulnerable to this second injury.

Ischaemic skeletal muscle hyperaemia in the anaesthetized cat: no contribution of A2A adenosine receptors

1. The present study investigated the contribution of the A2A adenosine receptor subtype to the functional hyperaemia response evoked by muscle contraction in anaesthetized cats when muscle blood flow was limited. 2. Application of a stenosis reduced the hindlimb blood flow at rest from 9.67 +/- 1.80 to 5.53 +/- 0.91 ml min(-1) (kg body mass)(-1) and during muscle contraction from 36.80 +/- 2.55 to 11.11 +/- 1.19 ml min(-1) (kg body mass)(-1) (P < 0.001). The force produced by the extensor digitorum longus and tibialis anterior (EDL-TA) muscle groups was also reduced, from 9.66 +/- 0.56 to 4.10 +/- 0.4 N (kg muscle mass)(-1) (P < 0.01). 3. The selective A2A adenosine receptor antagonist ZM241385 (3 mg kg(-1), I.V.) had no effect upon the hindlimb vascular conductance or muscle contraction responses in the presence of the flow-limiting stenosis. 4. In contrast, in the absence of the flow restriction the vascular conductance response was reduced by 27.5 +/- 5.0% (P < 0.05), whilst the isometric force produced by the EDL-TA muscle group was unaffected (pre- vs. post-contraction, 5.8 +/- 0.8 vs. 4.6 +/- 1.0 N (kg muscle mass)(-1) contraction). Oxygen consumption by the contracting hindlimb muscles was maintained (1.71 +/- 0.25 vs. 1.69 +/- 0.26 ml min(-1) (kg body mass)(-1)) by an increase in the oxygen extraction (51.9 +/- 4.9 vs. 66.2 +/- 6.1%; P< 0.01). 5. These results confirm previous data showing that adenosine, acting at the A2A receptor subtype, can contribute up to 30% of the functional hyperaemia response in the hindlimb of anaesthetized cats under free flow conditions. However, when blood flow is limited by a stenosis, antagonism of the A2A adenosine receptor does not affect functional hyperaemia.

Nerve entrapment syndromes

Peripheral nerve entrapment syndromes may be caused by inflammation, trauma, or congenital deficits. Some entrapment neuropathies are overdiagnosed, particularly carpal tunnel syndrome. Other nerve entrapment syndromes, such as the thoracic outlet syndrome, posterior interosseous nerve syndrome, and anterior interosseous nerve syndrome, are rare. In most cases of an entrapment neuropathy, the diagnosis and management are straightforward, but much remains to be learned about the natural history, course, and prevention of these clinical conditions.

Clinical and prognostic features in unilateral femoral neuropathies

We have examined the clinical features of patients with femoral neuropathy and the factors that influence the prognosis. Of 80 consecutive patients referred for neurophysiological evaluations of proximal lower limb weakness, 32 fulfilled strict inclusion criteria and had adequate information, including estimates of axon loss (AxL) by stimulation of the bilateral femoral nerve. In 31, the Kaplan-Meier method was used to describe the time course of the outcome, while logistic regression was employed to determine the contributing factors. Excellent, satisfactory, and poor outcomes were seen in 10 (31%), 11 (34%), and 10 (31%) patients, respectively. Logistic regression analysis of seven factors demonstrated that the estimate of AxL was the only significant variable. The best prognostic factor was an estimate of AxL < or = 50%, with all patients fulfilling this criterion showing improvement with 1 year; fewer than half the patients with AxL > 50% should be expected to improve. This study clearly shows that, irrespective of the cause of femoral neuropathy, functional improvement is seen in 2 out of 3 patients within 2 years and that the estimate of AxL is the only factor influencing prognosis.

Strain differences in autotomy levels in mice: relation to spinal excitability

The consequences of combined transection of the sciatic and femoral nerves were investigated in mice of the ICR and C3HEB strains. Whereas all the animals of the C3HEB strain showed very clear self mutilatory behavior of the denervated limb (autotomy) none of the ICR mice showed autotomy. Further tests, using the hot plate and tail flick methods, show that C3HEB mice were more sensitive to noxious thermal stimuli than ICR mice. Finally, spinalization at the lumbar level revealed a markedly higher level of spinal excitability in C3HEB mice as evident from a marked decrease in nociceptive thresholds in these animals. No such threshold decrease was observed in spinalized ICR mice. The results suggest that different levels of spinal excitability underlie the susceptibility for the emergence of autotomy in mice. It is proposed that such different levels of excitability may also underlie the susceptibility for the emergence of neuropathic pain.