Superficial radial sensory neuropathy: Medial and lateral branch injury

Description of an alternative method for the electrodiagnostic evaluation of the sensory radial nerve

OBJECTIVES

The aim of this study was to describe an alternative method for the electrodiagnostic (EDX) evaluation of the sensory radial nerve (SRN).

METHODS

In this retrospective study, all patients from a French EDX center (November 2022-April 2023) for whom SNAP amplitudes of the same SRN were obtained through both a conventional and an alternative method were included. In the conventional method, the active recording electrode was placed at the base of the snuff box, whereas in the alternative method, it was placed 3-4 cm proximally on the lateral border of the radial bone. The SNAP amplitudes of both methods were compared and the ratio of alternative to conventional amplitude was determined within the same patient. A secondary objective was to compare SNAP amplitudes and ratios between patients with peripheral neuropathy and those without (control group).

RESULTS

Among the 117 patients included, the mean ± SD SNAP amplitude was 50.0±28.9 µV in the alternative method compared to 31.0±17.9 µV in the conventional method. The ratio of alternative to conventional amplitudes was 1.64±0.4 in all patients. No significant difference in amplitude ratios was found between the peripheral neuropathy group (1.63 ± 0.4) and the control group (1.65 ± 0.3; p =0.75).

DISCUSSION

The alternative method, based on a more proximal placement of the recording electrodes, consistently provided larger SNAP amplitudes than the conventional method. This method could be useful in particular clinical settings but could prove more challenging in obese or muscular patients.

Radial neuropathy

Radial neuropathy is the third most common upper limb mononeuropathy after median and ulnar neuropathies. Muscle weakness, particularly wrist drop, is the main clinical feature of most cases of radial neuropathy, and an understanding of the radial nerve's anatomy generally makes localizing the lesion straightforward. Electrodiagnosis can help confirm a diagnosis of radial neuropathy and may help with more precise localization of the lesion. Nerve imaging with ultrasound or magnetic resonance neurography is increasingly used in diagnosis and is important in patients lacking a history of major arm or shoulder trauma. Radial neuropathy most often occurs in the setting of trauma, although many other uncommon causes have been described. With traumatic lesions, the prognosis for recovery is generally good, and for patients with persistent deficits, rehabilitation and surgical techniques may allow substantial functional improvement.

Clinical, Electrophysiological, and Sonographic Findings in Patients With Nerve Injury After Vessel Puncture

BACKGROUND AND PURPOSE

This study aimed to describe the clinical, electrophysiological, and ultrasonographic findings of patients with nerve injury after vessel puncture.

METHODS

Data on ten patients (three males and seven females) with nerve injury after vessel puncture were reviewed. Demographic and clinical data were analyzed retrospectively. Bilateral electrophysiological studies were performed based on clinical findings. Ultrasonographic examinations were performed on both the affected and unaffected sides of the injured nerve.

RESULTS

The nerves of nine patients were injured following vein puncture, and injury occurred following arterial sampling in one patient. Seven patients had superficial radial sensory nerve injury: five medial, one lateral, and one at both branches. One patient had injury to the dorsal ulnar cutaneous nerve, one to the lateral antebrachial cutaneous nerve, and one to the median nerve. Nerve conduction studies produced abnormal findings in 80% of patients, whereas ultrasonographic examinations produced abnormal findings in all of the patients. Spearman's coefficient for the correlation between the amplitude ratio and nerve cross-sectional area ratio was not significant, at -0.127 (95% confidence interval=-0.701 to 0.546, p=0.721).

CONCLUSIONS

Ultrasonography supported by electrodiagnosis was found to be a useful method for identifying the lesion location and structural abnormalities of vessel-puncture-related neuropathy.

Cheiralgia Paresthetica or Superficial Radial Sensory Mononeuropathy: A Simple Diagnosis, A Simple Solution, and a Side Note on the Pathophysiology of the Tinel Sign

We describe the case of a sculptor who developed superficial radial neuropathy (SRN) due to blunt trauma from striking a chisel for 30 years. The lesion was localized by the anatomical topography of the superficial radial nerve, a " hot " Tinel sign, and the graphic demonstration of reduced superficial radial sensory amplitude on a nerve conduction study (NCS). Our patient also responded to a strategically placed peripheral nerve block. We go further in this article and adumbrate on the underlying pathophysiology of the very Tinel sign we are so accustomed to, a clinical sign that is frequently deployed to diagnose a variety of peripheral nerve entrapments.

Utility of nerve conduction studies for diagnosis of injury to the medial branch of the superficial radial nerve

Introduction

The clinical utility of nerve conduction study (NCS) for the distal medial branch of the superficial radial nerve (SRN) has not yet been clarified. Therefore, we investigated the clinical utility of NCS in patients with suspected SRN injury and compared the results with those in healthy control subjects.

Methods

Bilateral NCS of the medial branch of the SRN was performed in two patients with suspected injury of the medial branch of the SRN, and in 20 healthy control subjects. A surface recording electrode was placed at the medial side of the metacarpophalangeal joint of the thumb. The SRN was then stimulated at a location 12 cm proximal from the recording electrode.

Results

The mean sensory nerve action potential in the two patients was significantly lower than that of the controls (6.75 ± 0.92 vs. 23.8 ± 8.2 μV, P < 0.05). The side-to-side differences in sensory nerve action potential in the two patients were significantly higher than in the controls (55 ± 7.1 vs. 11 ± 7.8%, P < 0.05).

Conclusions

NCS may be useful for diagnosing injury of the medial branch of the SRN.

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Nerve conduction was studied in the medial branch of the superficial radial nerve.

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The subjects were two patients with suspected medial branch injury and 20 controls.

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A recording electrode was placed at the medial side of the thumb.

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Mean sensory nerve action potential was lower in patients than controls.

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Nerve conduction study may be useful for diagnosing injury of the medial branch.