Slimmer's paralysis: electrophysiological evidence of compressive lesion

Slimmer’s palsy following an intermittent fasting diet

Background

Isolated common peroneal neuropathy (CPN) is the most common lower extremity mononeuropathy and the third most common mononeuropathy overall in adults. It often associated with multiple aetiologies, such as trauma, hereditary neuropathies and iatrogenic causes. We report a rare case of acute bilateral foot drop in a late adolescent female following a rapid weight loss attributable to intermittent fasting diet.

Case presentation

A 19-year-old female presented with worsening bilateral foot drop following a rapid intentional weight loss by intermittent fasting diet. She lost 20% of her baseline bodyweight within a period of 4 months. Systemic disease and metabolic screenings for neuropathy differentials were unremarkable. Electrophysiological studies revealed severe entrapment neuropathy involving bilateral common peroneal nerves (CPN). Her confounding risk factors for CPN injury include contact sport activities and habitual leg crossing during sitting. Following a dietary modification and physical therapy she achieved complete recovery of weakness and function on follow-up.

Conclusions

In a patient with bilateral PN rapid weight loss, prognosis is good and complete neurologic recovery can be attained through combination of cessation of extreme diet and physical therapy.

Varied Presentation and Importance of MR Neurography of the Common Fibular Nerve in Slimmer's Paralysis

Slimmer's paralysis refers to a common fibular nerve palsy caused by significant and rapid weight loss. This condition usually results from entrapment of the common fibular nerve due to loss of the fat pad surrounding the fibular head. Several etiologies of common fibular nerve palsy have been proposed, including trauma, surgical complications, improperly fitted casts or braces, tumors and cysts, metabolic syndromes, and positional factors. We present 5 cases of slimmer's paralysis in patients who had lost 32–57 kg in approximately 1 year. In 2 cases, MR neurogram of the knee demonstrated abnormalities of the common fibular nerve at the fibular head. Two patients underwent a common fibular nerve decompression at the fibular head and attained improved gait and sensorimotor function. Weight loss, diabetes mellitus, and immobilization may have contributed to slimmer's paralysis in 1 case. Awareness of slimmer's paralysis in patients who have lost a significant amount of weight in a short period of time is imperative to detect and treat a fibular nerve neuropathy that may ensue.

Factors that increase external pressure to the fibular head region, but not medial region, during use of a knee-crutch/leg-holder system in the lithotomy position

Background

Paralysis of the common peroneal nerve is one of the relatively common nerve injuries related to the lithotomy position with the use of a knee-crutch/leg-holder system. Several risk factors have been implicated in lithotomy position-related common peroneal nerve paralysis during operation.

Materials and methods

In the present study, 21 young healthy volunteers participated in the investigation of the causes of the paralysis of the common peroneal nerve in the lithotomy position using a knee-crutch/leg-holder; Knee Crutch. We assessed the external pressure applied to the fibular head and medial regions using the Big-Mat pressure-distribution measurement system. Relationships between the peak contact pressure and physical characteristics, such as sex, height, weight, body mass index (BMI), and fibular head circumference, were analyzed.

Results

The peak contact pressure to the fibular head region was greater for males than for females. For all subjects, significant positive correlations were observed between the peak contact pressure to the fibular head region and weight, BMI, or fibular head circumference. However, there was no significant difference between the peak contact pressure to the fibular head region and height for any subjects. Moreover, there was no sex-related difference in the peak contact pressure to the fibular medial region, and no significant differences between the peak contact pressure to the fibular medial region and height, weight, BMI, or fibular head circumference.

Conclusion

External pressure to the fibular head region is greater for males than for females using a knee-crutch/leg-holder system in the lithotomy position. In addition, the external pressure to the fibular head region, but not the fibular medial region, increases with increasing weight, BMI, and fibular head circumference. Therefore, these patient-related characteristics may contribute to the risk of developing lower-extremity neuropathy, leading to injury or ischemia of the common peroneal nerve.

Compression and entrapment neuropathies

Peripheral nerve entrapments are frequent. They usually appear in anatomical tunnels such as the carpal tunnel. Nerve compressions may be due to external pressure such as the fibular nerve at the fibular head. Malignant or benign tumors may also damage the nerve. For each nerve from the upper and lower limbs, detailed clinical, electrophysiological, imaging, and therapeutic aspects are described. In the upper limbs, carpal tunnel syndrome and ulnar neuropathy at the elbow are the most frequent manifestations; the radial nerve is less frequently involved. Other nerves may occasionally be damaged and these are described also. In the lower limbs, the fibular nerve is most frequently involved, usually at the fibular head by external compression. Other nerves may also be involved and are therefore described. The clinical and electrophysiological examination are very important for the diagnosis, but imaging is also of great use. Treatments available for each nerve disease are discussed.

Intraoperative electrophysiological studies to predict the efficacy of neurolysis after nerve injury-experiment in rats

Compound muscle action potentials (CMAPs) can be used to analyze injury and recovery of nerve. This standardized study evaluates the value of CMAP analysis in predicting the long-term efficacy of neurolysis. CMAP amplitude is also used to determine the optimal extent of neurolysis. The left peroneal nerves of 30 rats were crushed. CMAPs were recorded for both crushed (left) and control (right) nerves. Fifteen rats underwent neurolysis 3 months post crush injury; the remaining 15 were sham controls and did not undergo neurolysis. CMAP measurements were taken after: (1) release of the nerve from the fascia, (2) opening the epineurium, and (3) opening the perineurium. At 3 months post crush injury, opening the epineurium resulted in a statistically significant increase in CMAP. CMAP increase with perineurial neurolysis was greater than with fascial release of the nerve but was not statistically different from that of epineurial release. At 5 months post crush injury, recovery of crushed nerves that underwent neurolysis was 90% and significantly less at 70.5% in rats not treated with neurolysis, according to CMAP analysis. Two conclusions can be made from this study. First, intraoperative neurophysiologic studies can monitor the immediate results of neurolysis and predict long-term results in the injured nerve. Second, epineurotomy is important in neurolysis, improves the function of the nerve, less invasive, and a slightly more effective technique than perineurotomy.

Peroneal neuropathy following successful bariatric surgery

✓Peroneal neuropathy has been observed in starvation, anorexia, and other situations of extreme weight loss. The authors report a case in which sequential bilateral peroneal neuropathies developed after successful bariatric surgery resulting in a weight loss of 114 lbs over 12 months. The diagnosis was confirmed using nerve conduction studies and electromyography. Clinical improvement occurred with decompressive surgery at the level of the knee.

Diagnosis and management of common compression and entrapment neuropathies

The most common focal neuropathies are carpal tunnel syndrome, ulnar neuropathy at the elbow, and peroneal neuropathy at the fibular head, but many other focal neuropathies, due to external compression or entrapment, may occur. Rational management depends on accurate localization; a thorough understanding of the basic anatomy, pathology, and pathophysiology helps in dealing with the vagaries of clinical presentation and electrodiagnostic evaluation. The differential diagnosis includes musculoskeletal conditions, plexopathies, radiculopathies, and occasionally, central nervous system dysfunction. Some focal neuropathies are an accentuation of a more generalized process, and a complex interplay of focal and diffuse pathology can arise.

Pediatric peroneal mononeuropathy: a clinical and electromyographic study

Seventeen children with pediatric peroneal mononeuropathies evaluated between 1979 and 1991 are reported. Twelve boys and 5 girls, ranging in age from 1.5 months to 17 years, were referred for footdrop in 16 children (94%) or for lower extremity pain in 1 child (6%). Causes included compression in 10 children (59%), trauma in 3 children (18%), entrapment in 3 children (18%), and indeterminate in 1 child (5%). Based on nerve conduction studies and electromyography, the level of the pediatric peroneal mononeuropathic lesion was the common peroneal nerve in 10 children (59%), the deep peroneal nerve in 2 children (12%), and the superficial peroneal nerve in 1 child (5%). In 4 other children (24%), pediatric peroneal mononeuropathy at the knee was not more precisely identified. Surgical exploration in 3 children with progressive pediatric peroneal mononeuropathy was valuable. Improvement occurred in 13 of 17 children (76%).