Transgenic expression of human connexin32 in myelinating Schwann cells prevents demyelination in connexin32-null mice

Mutations in Gap Junction beta1 (GJB1), the gene encoding the gap junction protein connexin32 (Cx32), cause the X-linked form of Charcot-Marie-Tooth disease (CMT1X), an inherited demyelinating neuropathy. We investigated the possibility that the expression of mutant Cx32 in other cells besides myelinating Schwann cells contributes to the development of demyelination. Human Cx32 was expressed in transgenic mice using a rat myelin protein zero (Mpz) promoter, which is exclusively expressed by myelinating Schwann cells. Male mice expressing the human transgene were crossed with female Gjb1/cx32-null mice; the resulting male offspring were all cx32-null (on the X chromosome), and one-half were transgene positive. In these transgenic mice, all of the Cx32 was derived from the expression of the transgene and was found in the sciatic nerve but not in the spinal cord or the liver. Furthermore, the Cx32 protein was properly localized (within incisures and paranodes) in myelinating Schwann cells. Finally, the expression of human Cx32 protein "rescued" the phenotype of cx32-null mice, because the transgenic mice have significantly fewer demyelinated or remyelinated axons than their nontransgenic littermates. These results indicate that the loss of Schwann-cell-autonomous expression of Cx32 is sufficient to account for demyelination in CMT1X.

Advanced glycation endproducts in peripheral nerve in type 2 diabetes with neuropathy

Advanced glycation endproducts (AGE) accumulate over proteins as a consequence of diabetic hyperglycemia, and thus contribute to the pathogenesis of diabetic complications. To improve the understanding of the pathology of diabetic neuropathy, AGE accumulation was analyzed in sural and/or femoral nerves obtained under spinal anesthesia from 8 type 2 diabetic patients with both distal symmetrical polyneuropathy and proximal neuropathy. Pronounced AGE immunoreactivity was detected on axons and myelin sheaths in 90% of diabetic peripheral nerves but not in the control specimen. The intensity of axonal AGE immunopositivity significantly correlated with the severity of morphological alterations (p<0.005). AGE localization, demonstrated by immunohistochemical methods, was also present in the endoneurium, perineurium and microvessels. Morphometric analysis of the diabetic peripheral nerve showed perineurial thickening (diabetic vs. control, 15.5+/-4.9 vs. 6.6+/-2.1 microm, p<0.001), narrowing of the microvessel lumina (66.6+/-50.5 vs. 579.5+/-38.4 x10(3) microm(2), p<0.001) and significant reduction in the number of preserved axons (3.6+/-3 vs. 8.9+/-2.3 per 10(5) microm(2) per area, p<0.037). The sera of diabetic patients contained epitope(s) of AGE structure and soluble immune complexes containing AGE moiety. In conclusion, to the best of our knowledge, this is the first study providing evidence for excessive AGE formation on peripheral nerve components, primarily axons, and a significantly higher level of circulating AGE-immune complexes in patients with both distal diabetic polyneuropathy and proximal neuropathy. Humoral immune mechanisms, including the production of anti-AGE autoantibody, may potentially be involved in the development of structural abnormalities described in this report.

[Mild type of hemophilic pseudotumor with injury of femoral nerve (one case report)]

To explore the diagnoses and treatment of hemophilic pseudotumor, one case with hemophilic pseudotumor misdiagnosed and treated by operation, was observed and analyzed. The result showed that the final diagnosis of this case was following: hemophilia A (mild type) and hemophilic pseudotumor with injury of femoral nerve. The final diagnosis was given from inquiring case history and family history additionally, and drawing assistance from laboratory examination and computed tomography. After operation, the patient's wound healed very well through supplying coagulation factors positively. In conclusion, it was important for inquiring case history and family history particularly and thinking highly of laboratory examination to reduce the misdiagnosis and error of therapy for this case. If paying attention to preoperative preparation, the danger of hemorrhage during operation can be reduced and wound after operation can heal more rapidly.

Intrapelvic and thigh-level femoral nerve lesions: management and outcomes in 119 surgically treated cases

OBJECT

The authors present a retrospective analysis of 119 surgically treated femoral nerve lesions at intrapelvic and thigh levels seen at the Louisiana State University Health Sciences Center.

METHODS

Femoral nerve lesions treated between 1967 and 2000, (89 traumatic injuries and 30 tumors and cystic lesions) were evaluated for injury mechanisms, resulting lesions, surgical management, and postoperative functional outcomes by using retrospective chart reviews. The most common injury mechanism was iatrogenic (52 cases), which occurred after hernia and hip operations (10 each), followed by arterial bypass and gynecological procedures (eight each), angiography (seven), abdominal surgery (five), appendectomy (two), a laparoscopy, and a lumbar sympathectomy. Other injury mechanisms included hip or pelvic fractures (19), gunshot wounds (10), and lacerations (eight). The 30 femoral nerve tumors and cystic lesions consisted of neurofibromas (16), schwannomas (nine), ganglionic cysts (two), neurogenic sarcomas (two), and a leiomyosarcoma. Forty-four patients underwent neurolysis. Some had recordable nerve action potentials (NAPs) across their lesions in continuity, despite severe distal loss. Others with recordable NAPs had mild loss, but also experienced a pain problem, which was helped in some by neurolysis. In 36 patients, in whom repairs were performed using long sural grafts for mostly proximal pelvic-level injuries, recovery of useful function occurred. Eight of nine thigh-level suture repairs led to improvement to good functional levels. Most of the tumors and cystic lesions were resected, with preservation of preoperative function.

CONCLUSIONS

The majority of femoral nerve injuries resulted in lesions in continuity, and intraoperative NAP recordings were essential in evaluating axonal regeneration across these lesions. Despite severe and frequently proximal injury levels requiring repairs with long grafts, femoral nerve lesion repairs resulted in good functional recovery.

Lateral femoral cutaneous neuralgia: an anatomical insight

A detailed anatomic study was carried out on the lateral femoral cutaneous nerve to better understand the etiology and treatment of lateral femoral cutaneous neuralgia. As it passed from the pelvis into the thigh, the lateral femoral cutaneous nerve ran through an "aponeuroticofascial tunnel," beginning at the iliopubic tract and ending at the inguinal ligament; as it passed through the tunnel, an enlargement in its side-to-side diameter was observed, suggesting that the fascial structures proximal to the inguinal ligament may be implicated in the genesis of lateral femoral cutaneous neuralgia. The finding of pseudoneuromas at this location, distant from the inguinal ligament, supports this hypothesis. The anterior superior iliac spine is located approximately 0.7 cm from the lateral femoral cutaneous nerve and serves as the bony landmark for nerve localization. Within the first 3 cm of leaving the pelvis, the lateral femoral cutaneous nerve was observed deep to the fascia lata; therefore, surgical dissection within the subcutaneous fascia may be conducted with relative impunity near the anterior superior iliac spine just inferior to the inguinal ligament. In 36% of cases there was no posterior branch of the nerve, which is correlated to lateral femoral cutaneous neuralgia symptoms often being limited to the anterior branch region. An accessory nerve was found in 30% of cases.

Effect of lithotomy positions on strain of the obturator and lateral femoral cutaneous nerves

The purpose of this study was to determine if various lithotomy positions increase strain on the obturator and lateral femoral cutaneous nerves in fresh adult cadavers. A static load cell was used to record strain changes of the obturator and lateral femoral cutaneous nerves in the pelvis and anterior thigh when the lower limbs were placed in three sets of positions of varying hip abduction and flexion. The means of the strain measurements, which were measured in grams in all positioning angles were compared to the baseline 0 degrees measurements. Analysis of variance was calculated for the differences. Flexion of the hip did not increase strain on either nerve. Abduction to 30 degrees or 45 degrees increased strain by more than 30 g on the obturator nerve (P < 0.05) but not the lateral femoral cutaneous nerve. The addition of 45 degrees or more of flexion to abduction negated the strain increase on the obturator nerves seen with abduction alone. Nerve strain >30 g has been associated consistently with nerve dysfunction, disrupting axonal transmission, and causing structural neural damage. Our findings suggest that concomitant hip flexion should be used when placing anesthetized patients in a lithotomy position that includes abduction of the lower limbs to >30 degrees to decrease the risk for perioperative neuropathy of the obturator nerve.

[Extensive multinodular schwannoma of femoral nerve]

HISTORY AND PHYSICAL EXAMINATION

A 34-year-old woman contacted her general practitioner due to increasing circumference of her right thigh combined with occasional pain. The physical examination showed multiple nodular masses both in the groin and along the thigh that were painful to touch. The remainder of the physical examination was unremarkable.

DIAGNOSIS, THERAPY, AND CLINICAL COURSE

Both on ultrasonography and magnetic resonance imaging (MRI) a nodular mass was found on the right thigh extending from the groin to the inner side of the knee. A tissue biopsy with histological reviewing led to the diagnosis of a benign schwannoma. The following operation and clinical course went without major complications.

CONCLUSION

Peripheral schwannomas are rare, benign tumors of the nerve sheath usually appearing as round or oval masses. A schwannoma along the femoral nerve with an atypical shape of small diameter and an extension over a few decimeters has not been recorded yet. In spite of the length it is possible to treat schwannomas surgically without serious, permanent damage to the involved nerve.

Pediatric meralgia paresthetica

Meralgia paresthetica is a focal peripheral neuropathy involving the lateral femoral cutaneous nerve and is rarely observed in pediatric practice. Previous reports have highlighted its occurrence within the context of a regional bony malignancy. We present here three patients less than 18 years of age with idiopathic meralgia paresthetica.

Morphometric analysis of the human femoral nerve and its ageing process

We analysed the sizes of nerve fibres in the human femoral nerve which innervates the quadriceps femoris muscles. The material was taken from 14 cadavers aged from 61 to 97 years. A linear regression analysis disclosed a significant age-related decrease of the mean transverse area of axons. Such decrease with age may be an indication of motoneuron atrophy. Our results could help in the understanding of the correlation between morphology and function during the ageing process.

Secondary amyloidosis as a life-ending event in multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is a disorder of peripheral nerve often associated with a high monosialoganglioside (GM1) antibody and multifocal conduction block. It has a chronic, indolent course with involvement of predominantly peripheral motor nerves, usually in an asymmetric fashion. There have been few reported cases of progression to frank quadriplegia. Secondary amyloidosis refers to the deposition of amyloid in various tissues due to an underlying chronic inflammatory state. We report the first case, to our knowledge, of a patient with MMN associated with high titer of GM1 antibody who developed acute paraplegia with both cranial nerve and worsening sensory involvement associated with multiorgan compromise due to a secondary amyloidosis involving the myocardium.

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.

Use of enhanced stimulation voltage to determine the severity of compressive peripheral nerve injury

BACKGROUND

The aim of this study was to investigate whether enhanced stimulation voltage could be a predictor of the extent of injury in acute compressive peripheral nerve trauma.

METHODS

The femoral nerves were exposed on both sides, in 11 anesthetized rabbits. Supramaximal stimulation voltage was used to produce a maximal-amplitude compound muscle action potential (CMAP) from the quadriceps femoris muscle. Afterward, the left femoral nerve was clipped for 1 minute, and the right femoral nerve for 5 minutes to produce an acute compressive injury. Immediately after removal of the clip, the proximal and distal sides of the clippage site were stimulated by gradually increased voltage until CMAPs were obtained. The same procedure was repeated at the 30th and 60th minutes. The ratio of the CMAP amplitudes obtained from proximal and distal stimulation was measured to establish a classification.

RESULTS

The stimulation voltages and amplitudes of the CMAPs before clippage were similar with the after-clippage values obtained from distal stimulation (p > 0.05), but the after-clippage values obtained from proximal stimulation were different in both sides (p < 0.05). Doubled stimulation voltage was enough to obtain CMAPs on the left side, but eightfold the initial level was required on the right side. The amplitude ratios recovered to preinjury levels in all of the subjects on the left side, but only two showed recovery on the right side (p < 0.001). Histopathologically, there was axonal compression without discontinuity on the left side, whereas the fibers were dispersed on the right side.

CONCLUSION

Stimulation voltage was found to discriminate the severity of the lesion in experimental peripheral nerve injury. Proximal to distal amplitude ratio seems to be a prognostic factor when the injury is less severe.

Metastatic cardiac myxoma

A 22-year-old woman who had a history of three cardiac operations and a bilateral femoral embolectomy for recurrent cardiac myxoma and myxoma embolism, respectively, was accepted to our clinic with multiple immobile peripheral masses. One of them was compressing the left common femoral artery. This mass was extirpated. Pathology examination revealed myxoma. Chemotherapy was given to the patient and regression of the masses was observed.

Intercostal nerve neurotization of the femoral nerve in patients with paraplegia--an anatomical feasibility study

Neurotization of the brachial plexus is an established procedure in the upper limb. However, neurotization of the lower limb remains experimental. Brunelli reported the use of the ulnar nerve to neurotize the lower limb. Zhao et al reported the use of intercostals nerve to neurotize the lower limb in rats. The aim of the study was to determine the feasibility of using intercostals nerve to neurotize the femoral nerve in human cadavers and to ascertain the ideal intercostals nerve that has the anatomical course that suit this role. Six fresh cadaveric dissection were performed through an extensile midline incision in the postmortem room and the lower six (T7-T12) were identified and traced from their origin. Their length and course identified and charted. T9 and T10 intercostal nerve was thought to be the most suitable nerve as the donor nerve, and the T11 and T12 intercostal nerve could not be free from its intra-muscular course sufficiently to be use as donor.

Iliopsoas hematoma with femoral neuropathy presenting a diagnostic dilemma after spinal decompression

STUDY DESIGN

Case report of an iliopsoas hematoma with femoral neuropathy appearing 8 weeks after a posterior spinal decompression procedure.

OBJECTIVES

To describe a potential complication and differential diagnosis for nerve root symptoms following spinal decompression.

SUMMARY OF BACKGROUND DATA

Iliopsoas hematoma is usually a complication of anticoagulation, hemophilia, or trauma. It has not been described previously as a complication of posterior spinal decompression. Femoral neuropathy results from compression within the iliopsoas compartment.

METHODS

A 53-year-old woman reported pain in the right side of her groin and an increasing fixed flexion deformity of the right hip 8 weeks after a posterior, midline, spinal decompression. A femoral neuropathy later developed. Magnetic resonance imaging and computed tomography were performed.

RESULTS

Imaging studies demonstrated a diffusely enlarged iliopsoas. Exploration revealed a large hematoma, which was evacuated. The compartment was fully decompressed with resolution of the nerve root symptoms within 48 hours.

CONCLUSIONS

Iliopsoas pathology is a rare cause of nerve root symptoms and presented diagnostic difficulties after an apparently successful spinal decompression.

Malignant peripheral nerve sheath tumors in the setting of segmental neurofibromatosis. Case report

Approximately 100 cases of segmental neurofibromatosis (NF5) have been reported in the recent literature. Patients with NF5 present with café-au-lait macules, freckles, and/or neurofibromas limited to one or adjacent dermatomes. Neurofibromas arising in NF5 have been uniformly considered to be benign; patients were thought to have an excellent prognosis without the risk of developing malignant peripheral nerve sheath tumors (PNSTs), which are characteristic in patients with the generalized form of this disease, von Recklinghausen's NF. In this report the authors detail the first observations of malignant PNSTs in two patients with NF5. Indications for surgical removal of a neurofibroma in a patient with NF include pain. neurological impairment, compression of adjacent structures, cosmetic disfigurement, and rapid tumor growth suggestive of malignant degeneration. Surgical indications are similar for patients with NF5. All patients with neurofibromas should be considered at risk for malignant degeneration.

Iliopsoas haemophiliac pseudotumours with bowel fistulation

Two cases of iliopsoas haemophilic pseudotumours are presented. In one patient a fistula developed between a pseudotumour and the large bowel. This resulted in an abscess involving the pseudotumour and adjacent tissues. It resolved after 5 years of therapy involving percutaneous drainage and closure of the fistula. The second patient had a massive pseudotumour that had obstructed both ureters. Later he suffered a fatal mixed Gram negative septicaemia probably related to erosion into the colon.

Mechanoreceptors in collateral knee ligaments: an animal experiment

The mechanoreceptors in the collateral ligaments of the knee joint in rat hindlimbs were studied. In group II (n=10) the femoral and obturator nerves were sectioned. In both groups III and V (n=20) the sciatic nerve was sectioned. In group V (n=10) the sectioned sciatic nerve was sutured 4 weeks after sectioning. In group IV (n=10) all three nerves were sectioned. Group I (n=10) served as control. After 4 months all animals were killed. The ligaments of the knee joint were preserved and stained with gold chloride, paraffin-embedded and cut in sagittal serial sections. The results showed that 4 months after partial or total denervation of the limb, there was necrosis and a decrease in the number of mechanoreceptors, which was dependent upon the severity and site of the lesion. After suture of the sciatic nerve the increase in mechanoreceptors suggested a regenerative process.

Loss of distal axons and sensory Merkel cells and features indicative of muscle denervation in hindlimbs of P0-deficient mice

Mice lacking the major Schwann cell myelin component P0 show a severe dysmyelination with pathological features reminiscent of the Déjérine-Sottas syndrome in humans. Previous morphological and electrophysiological studies on these mice did not only demonstrate a compromised myelination and myelin maintenance, but were suggestive of an impairment of axons as well. Here, we studied the axonal pathology in P0-deficient mice by quantitative electron microscopy. In addition, we investigated epidermal receptor end organs by immunocytochemistry and muscle pathology by histochemistry. In proximal sections of facial and femoral nerves, axon calibers were significantly reduced, whereas the number of myelin-competent axons was not diminished in 5- and 17-month-old P0-deficient mice. However, in distal branches of the femoral and sciatic nerve (digital nerves innervating the skin of the first toe) the numbers of myelin-competent axons were reduced by 70% in 6-month-old P0-deficient mice. Immunolabeling of foot pads revealed a corresponding loss of Merkel cells by 75%, suggesting that survival of these cells is dependent on the presence or maintenance of their innervating myelinated axons. In addition, quadriceps and gastrocnemius muscles showed pathological features indicative of denervation and axonal sprouting. These findings demonstrate that loss of an important myelin component can initiate degenerative mechanisms not only in the Schwann cell but also in the distal portions of myelinated axons, leading to the degeneration of specialized receptor end organs and impairment of muscle innervation.

Studies in transgenic mice indicate a loss of connexin32 function in X-linked Charcot-Marie-Tooth disease

X-linked Charcot-Marie-Tooth disease (CMTX) is an inherited demyelinating neuropathy caused by mutations in the gene encoding the gap junction protein connexin32 (Cx32). Despite the identification of over 160 different mutations in the Cx32 coding sequence, it is not known whether the mutations cause the disease manifestations through a loss of Cx32 function or through toxic effects on peripheral nerve. We created transgenic mice with a frameshift mutation at codon 175 (175fs), identified in a large CMTX pedigree. Light microscopic examination of the peripheral nerves from adult transgenic animals showed no pathological features. Western blotting did not show transgenic Cx32 protein in any of the 26 lines, although expression of transgenic messenger RNA was detected by reverse-transcriptase polymerase chain reaction and by ribonuclease protection assay. Our findings indicate that the 175fs mutation results in a loss of Cx32 function, without additional toxic effects.

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.

Localized hypertrophic mononeuropathy involving the femoral nerve

The authors report a case of localized hypertrophic mononeuropathy involving the femoral nerve in a 20-year-old woman referred because of progressive weakness and atrophy of the left thigh. MRI showed an enlarged femoral nerve and biopsies of fascicles displayed a concentric pattern of cells resembling an onion bulb. These cells were positive for epithelial membrane antigen immunostaining and had an incomplete basal lamina.

Localized hypertrophic neuropathy: magnetic resonance imaging findings and long-term follow-up

Four patients with painless, progressive focal neurological deficits that localized to peripheral nerve or plexus were eventually found to have the relatively rare condition of localized hypertrophic neuropathy or intraneural perineurioma. Magnetic resonance imaging (MRI) was an excellent tool for aiding in the precise localization of the lesion, if specifically tailored with regard to imaging planes and specific MRI sequences. Fat-saturated T2-weighted and fat-saturated T1-weighted postgadolinium images provided the best visualization, particularly with a high-field magnet and phase array body coil. Two patients stabilized following resection of the lesion and sural nerve grafting, and 1 had partial improvement in a proximal muscle following neurolysis.