Motor neuron regeneration accuracy: balancing trophic influences between pathways and end-organs

The key to recovery of function following peripheral nerve lesions is guiding axons back to their original target end-organs. The parent femoral nerve splits into two comparable terminal pathways: one to the muscle and the other to the skin. Normally, motor neurons only innervate the pathway to the muscle, but after the parent nerve is repaired regenerating motor neurons are often misrouted to the skin. When the muscle and skin pathways remain connected to their respective targets after the parent nerve is repaired, reinnervation favors the muscle pathway. If contact with the muscle is instead prevented, reinnervation favors the pathway to the skin. Here we examine whether shortening the skin pathway can alter motor reinnervation accuracy when the muscle pathway remains connected to the muscle. We demonstrate that reducing the influence of the skin pathway results in a more rapid and extensive reinnervation of the muscle pathway. These findings suggest that the relative balance of trophic influences from the pathways and their end-organs is an important determinant of motor neuron regeneration accuracy, and that the muscle pathway by itself is not the primary regulator for regeneration accuracy of motor neurons.

The specificity of motor neurone regeneration (preferential reinnervation)

The major determinant of functional recovery after lesions in the peripheral nervous system is the accurate regeneration of axons to their original target end-organs. Unfortunately, regenerating motor axons are often misrouted to sensory target end-organs, and sensory axons formerly innervating skin are often misrouted to muscle. As such regeneration is robust, but often inaccurate, a better understanding of how regenerating axons reinnervate terminal pathways would be of fundamental interest to basic and clinical neuroscience. This review will consider the underlying cellular and molecular mechanisms that influence the accuracy of peripheral nerve regeneration, within the context of 'preferential motor reinnervation' (PMR). Much previous work with PMR has utilized the rodent femoral nerve and has shown that regenerating motor axons preferentially, albeit incompletely, reinnervate a distal terminal nerve branch to muscle (quadriceps) vs. skin (saphenous). One interpretation of this body of work has been that Schwann cell tubes have a specific identity that can be recognized by regenerating motor axons and that influences their subsequent behaviour. We disagree with that interpretation, and suggest motor and cutaneous pathways are not inherently different in terms of their ability to support regeneration of motor axons. In fact, recent experiments indicate under certain conditions motor axons will preferentially reinnervate the inappropriate terminal cutaneous pathway instead of the appropriate pathway to muscle. We suggest that it is the relative level of trophic support provided by each nerve branch that determines whether motor axons will remain in that particular branch. Within the context of the femoral nerve model, our results suggest a hierarchy of trophic support for regenerating motor axons with muscle contact being the highest, followed by the length of the terminal nerve branch and/or contact with skin.

Characterization of chronic constriction of the saphenous nerve, a model of neuropathic pain in mice showing rapid molecular and electrophysiological changes

Neuropathic pain is one of the most inextricable problems encountered in clinics, because few facts are known about its etiology. Nerve injury often leads to allodynia and hyperalgesia, which are symptoms of neuropathic pain. The aim of this study was to understand some molecular and electrophysiological mechanisms of neuropathic pain after chronic constriction of the saphenous nerve (CCS) in mice. After surgery, CCS mice displayed significant allodynia and hyperalgesia, which were sensitive to acute systemic injection of morphine (4 mg/kg), gabapentin (50 mg/kg), amitriptyline (10 mg/kg), and the cannabinoid agonist WIN 55,212-2 (5 mg/kg). These behavioral changes were accompanied after surgery by an increase of c-Fos expression and by an overexpression of mu-opioid and cannabinoid CB1 and CB2 receptors in the spinal cord and the dorsal hind paw skin. In combination with the skin-nerve preparation, this model showed a decrease in functional receptive fields downstream to the injury and the apparition of A-fiber ectopic discharges. In conclusion, CCS injury induced behavioral, molecular, and electrophysiological rearrangements that might help us in better understanding the peripheral mechanisms of neuropathic pain. This model takes advantage of the possible use in the future of genetically modified mice and of an exclusively sensory nerve for a comprehensive study of peripheral mechanisms of neuropathic pain.

Nerve conduction studies of the lateral femoral cutaneous nerve. Implications in the diagnosis of meralgia paresthetica

The diagnosis of meralgia paresthetica, while based on clinical suspicion, can be confirmed via electrophysiological testing. Previous testing of the sensory conduction of the lateral femoral cutaneous nerve placed the stimulating electrode one centimeter medial to the anterior superior iliac spine (ASIS). This position is both uncomfortable for the patient and difficult for the operator to perform. The following article suggests an alternate position for the stimulating electrode, four centimeters distal to the ASIS. Twenty subjects served as their own controls and both the old technique and the new technique were performed. Using the old technique, the response rate was 35% (7 out of 20 subjects). Using the new technique, the response rate was 90% (18 out of 20 subjects). These results indicate a significantly higher response rate when the only variable altered is the electrode placement. This simple change in technique requires no more effort, cost, or training on the part of the operator yet produces a much higher percentage of responses.

Electrophysiological evaluation of the genitofemoral nerve in patients with inguinal hernia

Groin pain in the lower abdomen but including the ilioinguinal region is frequent after inguinal hernia operations, but the integrity of the nerves in this region, including the genitofemoral nerve (GFN), has not been investigated. We studied GFN motor conduction time to the cremasteric muscle (CM), the CM electromyogram (EMG), and the CM reflex in 30 patients with unilateral inguinal hernia who underwent herniorrhaphy and in 26 similar patients who had no surgical intervention. Among the 30 patients undergoing herniorrhaphy, 14 (47%) showed motor involvement of the GFN, whereas 6 of the 26 (23%) patients not treated surgically had involvement of the GFN. These findings indicate that subclinical motor involvement of the GFN can be demonstrated by electrophysiological methods and is common after inguinal herniorrhaphy. Based on patient complaints, the herniated mass may also be responsible for motor involvement of the GFN in some patients before surgery.

[A role of central control in development and progression of diabetic polyneuropathy in teenagers]

A role of central control of peripheral nervous system was investigated in 79 teenagers with noninsulin-dependent diabetes mellitus. The patients were studied using clinical and neurophysiological methods, electroneuromyography and somatosensory evoked potentials (SSEP). The SSEP analysis revealed the disturbances of sensory pathways in the central nervous system at early stage of diabetes mellitus. A new pathogenic mechanism of progressive polyneuropathy with trophic complications is presented. At the initial stage of the disease, low conductivity is combined with a compensating acceleration of conductivity in the central structures. In diabetes course, central conductivity declines and control over peripheral system decreases resulting in the disease progression. In trophic complications, acceleration of conductivity is absent already at the early stages, suggesting a primary weak control over the peripheral nervous system.

Assessment of low-frequency fatigue with two methods of electrical stimulation

The aim of this study was to compare the use of transcutaneous vs. motor nerve stimulation in the evaluation of low-frequency fatigue. Nine female and eleven male subjects, all physically active, performed a 30-min downhill run on a motorized treadmill. Knee extensor muscle contractile characteristics were measured before, immediately after (Post), and 30 min after the fatiguing exercise (Post30) by using single twitches and 0.5-s tetani at 20 Hz (P20) and 80 Hz (P80). The P20-to-P80 ratio was calculated. Electrical stimulations were randomly applied either maximally to the femoral nerve or via large surface electrodes (ES) at an intensity sufficient to evoke 50% of maximal voluntary contraction (MVC) during a 80-Hz tetanus. Voluntary activation level was also determined during isometric MVC by the twitch-interpolation technique. Knee extensor MVC and voluntary activation level decreased at all points in time postexercise ( P < 0.001). P20 and P80 displayed significant time × gender × stimulation method interactions ( P < 0.05 and P < 0.001, respectively). Both stimulation methods detected significant torque reductions at Post and Post30. Overall, ES tended to detect a greater impairment at Post in male and a lesser one in female subjects at both Post and Post30. Interestingly, the P20-P80 ratio relative decrease did not differ between the two methods of stimulation. The low-to-high frequency ratio only demonstrated a significant time effect ( P < 0.001). It can be concluded that low-frequency fatigue due to eccentric exercise appears to be accurately assessable by ES.

High-frequency electrical stimulation of femoral nerve reduces infarct size following myocardial ischemia-reperfusion in rats

The effects of femoral nerve electrostimulation (FNES) on ischemia-reperfused myocardium were examined in the urethane- anesthetized rats to determine whether FNES may provide cardioprotection and to observe the possible mechanism. The area at risk (AR) and infarct area (IA) were determined using Evans blue and nitro-blue tetrazolium staining, respectively. Infarct size (IS) was defined as 100xIA/AR (%). The results are as follows: (1) During 30 min myocardial ischemia and subsequent 120 min reperfusion, the myocardial infarct size occupied (54.96+/-0.82)% of the area at risk. (2) FNES of high frequency (10 V, 100 Hz, 1 ms) significantly reduced myocardial infarct size to (36.94+/-1.34)% (P<0.01), indicating the cardioprotective effect FNES of high frequency on myocardial ischemia-reperfusion, while FNES of low frequency (10 V, 10 Hz, 1 ms) had no effect on myocardial infarct size. (3) Pretreatment with either naloxone (5 mg /kg, i.v), a nonselective opioid receptor antagonist, or glibenclamide (5 mg /kg, i.v), a K(ATP) channel antagonist, completely abolished the cardioprotection of FNES (100 Hz) from myocardial ischemia-reperfusion. It is suggested that FNES of high frequency can protect myocardium from ischemia-reperfusion injury. The possible mechanism is that FNES of high frequency may induce the release of opioids from the central nervous system, and the activation of opioid receptors in the heart results in an opening of myocardial K(ATP) channels which can protect myocardium.

Morbidity of harvesting of bone grafts from the iliac crest for preprosthetic augmentation procedures: A prospective study

It has been the aim of the present prospective clinical study to assess the morbidity following the harvest of bone from the anterior and posterior ilium in elective preprosthetic augmentations. Fifty consecutive healthy patients (30 female, 20 male, mean age 52.5+/-9.3 years, range 31 years to 65 years) underwent augmentations of implant sites by iliac crest bone grafts. The bone harvest was carried out in 25 cases from the anterior and in 25 cases from the posterior ilium. The superficial sensory function of the skin was determined quantitatively preoperatively, 7 and 30 days after surgery with the 'Pain and Thermal Sensitivity' Test (PATH Test). On the same occasions subjective pain on a visual analogue scale (VAS) and gait disturbances were documented. In the PATH Test, for the innervation areas of the lateral femoral cutaneous nerve (LFCN) and the superior and middle cluneal nerves (SMCN) a significant impairment of the superficial sensory function could be found after 1 week and a significant tendency towards recovery after 1 month (warm stimulus(FCNpreop) 37.9+/-3.0 degrees C, warm stimulus(LFCNday7): 38.6+/-3.2 degrees C, warm stimulus(LFCNday30): 37.9+/-2.9 degrees C, P(LFCNwarmpreop/day7)=0.023,P(LFCNwarmpreop/day30) =0.886, warm stimulus(SMCNpreop): 36.1+/-2.4 degrees C, warm stimulus(SMCNday7): 36.6+/-2.3 degrees C, warm stimulus(SMCNday30): 36.3+/-4.0 degrees C,P(SMCNwarmpreop/day7) <0.0005,P(SMCNwarmpreop/day30) =0.086). Gait disturbances were seen in seven patients after anterior and in three patients after posterior bone harvest 7 days after surgery (P(gaitdisturbanceanterior/posterior)=0.123). After 1 month none of the patients of both groups showed gait disturbances any longer. The maximum subjective pain level was found on the second postoperative day in both groups. It was significantly higher for the anterior approach (VAS(anteriorday2) 7.0+/-1.5, VAS(posteriorday2) 5.5+/-1.8,P(VASanterior/posteriorday2) =0.004). At day 7 and at day 30, the pain levels did no longer differ significantly (VAS(anteriorday7) 3.7+/-1.4, VAS(posteriorday7) 3.2+/-1.6,P(VASanterior/posteriorday7) =0.165, VAS(anteriorday30) 1.4+/-0.7, VAS(posteriorday30) 1.4+/-0.8,P(VASanterior/posteriorday30) =0.724). Because of the lower morbidity of bone harvest from the posterior ilium in the early postoperative phase compared to the anterior approach it seems that it should be preferred in elective augmentation procedures.

[Electrophysiological evaluation of peripheral nerves in ischemic lower limbs]

The study concerned electrophysiological parameters during stimulation of peroneal, tibial, sural and femoral nerves of patients with ischemia of lower limbs. The disease was clinically verified and confirmed on the basis of an ankle-brachial index (ABI). Peripheral nerves injuries caused by other reasons have been excluded from the research. For statistical evaluation of the material, groups of 86 chronic ischemic limbs (ABI < 0.91) and 57 healthy ones (ABI > 0.99) were created. All observation allowed to recognize an axonal-demyelization neuropathy, with strong axonal element. Changes concerned mainly long nerves. Coexistence of spinal roots damage was often (75.4%) noticeable. The correlation between degree of ischemia (ABI) and studied parameters has not been noticed. We described 5 cases of acute ischemia. There was no significant improvement after surgical or conservative therapy.

Somatosensory evoked potentials for the electrodiagnosis of meralgia paresthetica

The aim of this study was to evaluate the diagnostic utility of somatosensory evoked potential (SSEP) studies of the lateral femoral cutaneous nerve (LFCN) in assessing patients with meralgia paresthetica. Twenty-one consecutive patients with unilateral meralgia paresthetica, as defined clinically (sensory impairment of lateral aspect of the thigh) and electrodiagnostically (abnormal sensory nerve conduction), and 21 control subjects were studied with two SSEP methods. SSEPs were elicited by stimulation of the LFCN below the anterior superior iliac spine (ASIS stimulation) and by cutaneous stimulation of the lateral aspect of the distal third of the thigh (thigh stimulation). Abnormalities were defined by the SSEP interside latency difference, interside amplitude ratio, or an absent response. The SSEP with ASIS stimulation had a sensitivity of 5% and a specificity of 95%, whereas with thigh stimulation it had a sensitivity of 52% and a specificity of 76%. Overall, SSEP after ASIS stimulation had no diagnostic value. Recording of the SSEP after thigh stimulation is recommended in obese patients only when sensory nerve conduction cannot be determined.

Femoral, saphenous nerve palsy after tourniquet use: a case report

Persistent motor and sensory abnormalities after surgery may affect the rehabilitation process. Patients with continued weakness may be perceived as lacking motivation by health care providers. However, there may be an underlying pathophysiologic abnormality preventing patients from progressing through their rehabilitation programs. We report a case of a 20-year-old man who underwent surgical repair of multiple knee structures with the use of a pneumatic tourniquet. Several weeks after surgery, electromyographic evaluation was done because he was having difficulty in his rehabilitation because of persistent weakness. An electromyography and nerve conduction study (NCS) revealed femoral and saphenous nerve palsies. Our report is the first on tourniquet-induced saphenous nerve injury as well as on abnormal femoral NCSs caused by tourniquet use. A review of the literature indicates that tourniquet-induced nerve palsies are not a rare event. Further evaluation should be considered if patients who are having persistent weakness or sensory findings after surgery have used a tourniquet.

Cortical processing of brush-evoked allodynia

The cortical processing of allodynia (touch-evoked pain) resulting from neuralgia of the lateral cutaneous femoral nerve was investigated with a newly designed pneumatically driven brush by means of magnetoencephalography. Brushing the unaffected thigh produced subsequent activation of the contralateral primary somatosensory cortex (S1) with peak latencies of 37 and 56 ms. Brushing the affected side led to comparable activation of the contralateral S1 cortex. In addition, the magnetic fields were stronger, and the corresponding equivalent current dipoles were located more laterally, consistent with the presence of cortical reorganisation. Allodynia was also accompanied by an activation of the cingulate cortex, occurring only 92 ms. after stimulus onset, an observation suggesting an Abeta-fiber-mediated neuronal pathway involved in dynamic mechanical allodynia. This study corroborates the concept of cortical reorganisation underlying chronic pain. Furthermore, it demonstrates that a remarkable early activation of the cingulate cortex may be involved in the cortical processing of allodynia.

Treatment of meralgia paresthetica with a deep inferior epigastric perforator adiposal flap: case report

A case of a 40-year-old female with meralgia paresthetica after malignant tumor resection in the right inguinal region is reported. Traditionally, meralgia paresthetica is treated with neurotransection or neurolysis. The therapeutic strategy using neurolysis, and the use of a deep inferior epigastric perforator adiposal flap wrapping as a prophylactic procedure against reentrapment is discussed.

Effect of intrathecal clonidine on group I and group II oligosynaptic excitation in paraplegics

We investigated the possibility that a change in transmission in group II pathways contributes to the spasticity of patients with spinal lesions. Thirteen patients were tested by measuring the quadriceps stretch reflex (Ashworth scale), the threshold of the quadriceps H reflex, and the oligosynaptic facilitation of the quadriceps H reflex elicited by volleys to groups I and II afferents in the common peroneal nerve (CPN). All these tests were performed before and after intrathecal injection of clonidine (60 microg). Early group I CPN-induced excitations occurred in 13 patients, and late group II CPN-induced excitations in 12. Both facilitations were, on average, significantly greater than those reported for normal subjects, but these increases were not correlated with the clinically assessed spasticity. Clonidine caused a constant, prolonged and dramatic decrease in spasticity, but did not alter the threshold of the quadriceps H reflex. CPN-induced group I and group II non-monosynaptic excitations of quadriceps motoneurones were significantly decreased, although they did not return to normal values. These results provide a further indication that group II pathways gives rise to the heteronymous late CPN-induced excitation. The pathophysiological role of a change in transmission in group II pathways in spasticity is discussed.

Evoked potentials elicited by stimulation of the lateral and anterior femoral cutaneous nerves in meralgia paresthetica

Seventy-five consecutive patients with clinical symptoms and signs of meralgia paresthetica underwent bilateral somatosensory evoked potential (SEP) studies involving stimulation of skin areas innervated by the lateral and anterior femoral cutaneous nerves of the thighs. The most common abnormality was an absolute lateral femoral cutaneous SEP latency > 40 ms in 35 patients (47%), followed by an absent response in 14 patients (19%), an absolute latency < 40 ms but amplitude reduction > 50% compared with the contralateral response in 8 patients (11%), and an absolute latency < 40 ms but > 5 ms interside latency difference in 5 patients (7%). Anterior femoral cutaneous SEPs were of value in distinguishing meralgia paresthetica from a proximal lumbar radiculopathy in an additional 4 patients and confirming bilateral meralgia paresthetica in 10 patients.

[Prostaglandin inhibitor indomethacin inhibits afferent activities of Adelta and C units in the saphenous nerve of diabetic hyperalgesic rats]

The effects of a non-selective inhibitor of cyclo-oxygenase (COX) indomethacin, and exogenous prostaglandin E(2) (PGE(2)) on A(delta) units and C units in the saphenous nerve of diabetic hyperalgesic rats were studied. The results showed that the conduction velocity of A(delta) units and C units and their mechanical threshold in diabetic hyperalgesic rats were obviously decreased, and a small number of A(delta) units (4/24) and C units (2/18) produced increased spontaneous activities. Intraperitoneal injection of indomethacin in diabetic hyperalgesic rats significantly relieved mechanical hyperalgesia, and resulted in a decrease in spontaneous afferent activities of the A(delta) units and C units. Subcutaneous injection of exogenous PGE(2) into the diabetic hyperalgesic and control rats produced a significant decrease in mechanical threshold of the A(delta) units and C units, and elicited discharge from 3 A(delta) units (3/24) and 1 C unit (1/18) in diabetic hyperalgesic rats and from 2 A(delta) units (2/13) in control rats. The present data suggest that the synthesis and release of PGs are increased in diabetic neuropathy, PGs can sensitize and /or activate A(delta) units and C units and elicit hyperalgesia and allodynia in diabetic rats.

Contralateral genitofemoral sympathetic nerve discharge increases following ipsilateral testicular torsion

The decrease in blood flow due to the activation of sympathetic system has been suggested to play a role in contralateral testicular deterioration associated with unilateral testicular torsion. Sympathetic nerve discharges (SND) from the genitofemoral nerve were evaluated before and during unilateral testicular torsion. Under urethane anesthesia, arterial blood pressure and SND from splanchnic and right genitofemoral nerves were recorded in 12 male Sprague-Dawley rats, 8 of which were included in subsequent analyses. After control recordings of basal discharges for 2 min the left testis was twisted 720 degrees counterclockwise, and recording was resumed for an additional 30 min. Changes in nerve activity were calculated by measuring the area under the autospectrum curve, and alterations were compared. Following testicular torsion no significant changes were obtained for splanchnic SND, but the amplitude of SND from contralateral genitofemoral nerve showed an overall increase of 21.20+/-7.03% in six rats. This increase lasted about 10-15 min and activities returned to pretorsion levels. In two other rats no significant change was observed in either splanchnic or genitofemoral SND. Ipsilateral testicular torsion results in a transient increase in genitofemoral SND. A possible autonomic reflex mechanism may exist, and it may be activated by noxious stimuli from contralateral side. This reflex mechanism may initiate a series of events that lead to the injury of contralateral testis.

Altered vastii recruitment when people with patellofemoral pain syndrome complete a postural task

OBJECTIVE

To investigate the recruitment of the vastus medialis obliquus (VMO) and vastus lateralis during voluntary tasks that challenge the stability of the knee and to evaluate whether there is a change in the coordination of the postural response by the central nervous system in subjects with patellofemoral pain syndrome (PFPS).

DESIGN

Cross-sectional.

SETTING

University laboratory in Australia.

PARTICIPANTS

Thirty-seven subjects with PFPS and 37 asymptomatic sex-matched controls.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Recordings of electromyographic activity of the VMO, vastus lateralis, tibialis anterior, and soleus were made by using surface electrodes. Subjects rose onto their toes (rise task) or rocked back on their heels (rock task) in a visual choice-reaction time task. Electromyographic onsets were determined by using a computer algorithm and were verified visually.

RESULTS

Our results confirm that, in asymptomatic subjects, contraction of the VMO and vastus lateralis occurs as part of the feed-forward postural response associated with ankle movements in standing, and the contraction of these separate heads of the quadriceps group occurs simultaneously. However, when subjects with PFPS perform identical tasks, the electromyographic onset of the vastus lateralis occurs before that of the VMO.

CONCLUSION

These findings indicate a difference in motor control in subjects with PFPS. They also support the hypothesized relation between changes in the timing of activity of the vastii and PFPS and provide the theoretic rationale to support physiotherapy treatment commonly used in the management of PFPS.

[Clinical and neurophysiological features and outcome prognosis criteria of Guillain-Barre syndrome in children]

Clinical and electroneuromyographical (ENMG) study of 24 children with Guillain-Barre syndrome (GBS) was conducted. Using ENMG, axonal and demyelinating GBS variants differing by course and rehabilitation time were distinguished. To predict a development of bulbar and respiratory disorders and to evaluate their severity and duration, diaphragm and adductive nerves conduction was investigated. Factors influencing motor function rehabilitation rate in GBS were the following: mean distal M-response amplitude during peroneal nerve stimulation, proximal to distal amplitudes ratio, M-response amplitude for femoral nerves. Three types of ENMG parameter rehabilitation in children with GBS (linear, stepped and undular) which characterize different rates of rehabilitation process are described.

Effectiveness of femoral nerve selective block in patients with spasticity: preliminary results

OBJECTIVES

To determine if the vastus intermedius nerve can be blocked by using surface coordinates and to measure the effects of selective nerve block on quadriceps spasticity and immediate gait.

DESIGN

Case series.

SETTING

Physical medicine and rehabilitation department of a university hospital.

PARTICIPANTS

Twelve patients with hemiplegia disabled by quadriceps overactivity.

INTERVENTION

Anesthesic block of the vastus intermedius by using surface coordinates, femoral nerve stimulation before and after block, and surface electrodes recording of the amplitude of the maximum direct motor response of each head of the quadriceps.

MAIN OUTCOME MEASURES

Assessment of spasticity, voluntary knee extension velocity, speed of gait, and knee flexion when walking.

RESULTS

To be effective, the puncture point (.29 of thigh length and 2cm lateral) had to be slightly modified to 1cm laterally from a point situated at 0.2 of the thigh length. A selective block of the vastus intermedius could not be achieved, but a block of the vastus lateralis was always achieved, twice associated with a block of the vastus intermedius, resulting in decreased quadriceps spasticity, no changes in gait parameters, no decrease in voluntary knee extension velocity, and subjective improvement in gait for 3 patients.

CONCLUSION

Selective block of the vastus lateralis with or without the vastus intermedius can be achieved by using surface coordinates without any dramatic effect on knee extension velocity, and it could be useful for phenol or alcohol block or surgical neurotomy.

Meralgia paresthetica in differential diagnosis of low-back pain

OBJECTIVE

Meralgia paresthetica is a syndrome of pain or dysesthesia or both in the anterolateral thigh, caused by entrapment of the lateral femoral cutaneous nerve at the anterior superior iliac spine. The aim of this report is to emphasize that meralgia paresthetica can be confused with low-back pain.

PATIENT

A 21-year-old man was admitted to hospital because of low-back and thigh pain. He had a history of low-back pain. Physical examination and radiologic studies for low-back pain and radiculopathy showed no pathologic findings. It was suspected that the most likely cause was lateral femoral cutaneous neuropathy, caused by the wide military belt he continuously wore tightly around his waist.

INTERVENTIONS

The nerve was blocked with 10 ml of bupivacaine 0.25%, which provided immediate pain relief. A nonsteroidal anti-inflammatory drug was administered orally.

RESULTS

After 15 days of bed rest and 45 days without the belt, he was completely symptom-free.

CONCLUSIONS

It is important to be rigorous in investigating the etiology of low-back pain. Meralgia paresthetica can mimic low-back pain because of the similarity of the symptoms. It can be treated by conservative or ablative therapeutic interventions; however, conservative methods should be considered primarily.

Inflammation with no axonal damage of the rat saphenous nerve trunk induces ectopic discharge and mechanosensitivity in myelinated axons

Inflammation along a nerve trunk with no frank axonal nerve damage produced by complete Freund's adjuvant (CFA) or Carrageenan is known to induce a painful peripheral neuropathy. In the present study, we examined the electrophysiological properties of myelinated axons (spontaneous discharge and mechanical sensitivity) at the inflamed nerve site. The rat saphenous nerves were exposed at mid-thigh level and wrapped in 2 mm wide bands of haemostatic oxidized cellulose (Oxycel) that were saturated with undiluted CFA. In the control rats the Oxycel) was saturated with saline. At postoperative days (PODs) 2-5 and 6-10, fine axon bundles were teased from the nerve, and electrophysiological recordings performed. At both time points spontaneous activity at the site of the application in CFA rats (PODs 2-5=9.9+/-2.5%: PODs 6-10=6.1+/-1.4%) was significantly higher than in the control animals (PODs 2-5=2.9+/-1.1%: PODs 6-10=1.6+/-1.4%: P=0.03, P=0.02, respectively). Mechanical sensitivity at both time points was significantly higher in CFA rats (PODs 2-5=12.6+/-3.1%: PODs 6-10=10.3+/-3.1%) than in saline rats (PODs 2-5=3.4+/-2.91%: PODs 6-10=0.8+/-1.0%: P=0.03, P=0.04, respectively). This study clearly shows that perineural inflammation with no axonal nerve damage induced by CFA application around the nerve trunk elevates spontaneous activity and induces mechanosensitivity in myelinated axons.