Peripheral nerve injuries (PNIs) are common, costly, and cause significant pain. Effective management of PNIs involves tailoring medications to the injury type as well as understanding the pharmacokinetics/pharmacodynamics to support nerve regeneration and reduce pain. Opioids act on opioid receptors to significantly reduce pain for many patients, but there are significant addiction risks and side effects. In addition, opioids may exacerbate pain sensitivity and affect nerve regeneration. Non-steroidal anti-inflammatory drugs or acetaminophen act on cyclooxygenase enzymes and are commonly used for nerve pain, with 34.7% of people using them for neuropathic pain. While effective for mild pain, they are often combined with opioids, gamma-aminobutyric acid (GABA) analogs, lidocaine, or corticosteroids for more severe pain. Corticosteroids, mimicking adrenal hormones like cortisol, treat PNI-related inflammation and pain. Their pharmacokinetics are complex, often requiring local injections in order to minimize systemic risks while effectively treating PNIs. Lidocaine, a common local anesthetic, blocks ion channels in the central nervous system (CNS) and peripheral nerves, providing strong analgesic and anti-inflammatory effects. If used improperly, lidocaine can cause neuronal toxicity instead of anesthetic effect. GABA acts as an inhibitory neurotransmitter in the CNS and its drug analogs like pregabalin and gabapentin can alleviate neuropathic pain by binding to voltage-gated Ca2+ channels, inhibiting neurotransmitter release. These pain medications are commonly prescribed for PNIs despite a limited guidance on their effects on nerve regeneration. This review will discuss these drug's mechanisms of action, pharmacokinetics/pharmacodynamics, and their clinical application to highlight their effect on the PNI recovery.

Teaching point: Hourglass-like constrictive neuropathy should be considered in patients with unexplained peripheral neuropathy symptoms, as imaging may show nerve constriction without evidence of intrinsic or extrinsic compression.

Neuralgic amyotrophy, also called Parsonage-Turner syndrome, in its classic presentation is a brachial plexopathy or a multifocal neuropathy, involving mainly motor nerves of the upper limb with a monophasic course. Recently, a new radiological entity was described, the hourglass constriction, which is characterized by a very focal constriction of a nerve, or part of it, usually associated with nerve thickening proximally and distally to the constriction. Another condition, which is similar from a radiological point of view to hourglass constriction, is nerve torsion. The pathophysiology of neuralgic amyotrophy, hourglass constriction and nerve torsion is still poorly understood, and a generic role of inflammation is proposed for all these conditions. It is now widely accepted that nerve imaging is necessary in identifying hourglass constrictions/nerve torsion pre-surgically in patients with an acute mononeuropathy/plexopathy. Ultrasound and MRI are useful tools for diagnosis, and they are consistent with intraoperative findings. The prognosis is generally favorable after surgery, with a high rate of good motor recovery.

A 21-year-old collegiate baseball pitcher presented with transient lateral arm pain and wrist extension weakness after pitching more than 1 inning. Physical examination was unremarkable at rest. Ultrasound-guided injection of the radial nerve at the level of the lateral intramuscular septum improved his symptoms. After decompression of the radial nerve, the patient noted resolution of his symptoms while pitching.

Atraumatic radial neuropathy is a rare but documented phenomenon. As far as we know, this is the first reported case of a transient exertional radial neuropathy in an athlete at the level of the lateral intermuscular septum.

The purposes of this study were to determine reliable diffusion-weighted magnetic resonance neurography (DW-MRN) features of hourglass-like constriction of the upper limb nerve and to evaluate the application value of DW-MRN compared with ultrasonography (US).

We retrospectively reviewed MRN studies of 13 patients. Qualitative and quantitative image analyses were carried out. The number of constrictions based on DW-MRN and US findings was compared.

Of the 13 cases, there were 7 cases with radial nerve abnormalities, 4 with median nerve abnormalities, and 2 with radial and median nerve abnormalities. Diffusion-weighted MRN showed a single-segmental constriction in 7 of 13 cases and multisegmental constrictions in 6 of 13 cases; the hourglass-like constriction appeared in all cases (13 of 13). Thirty-three nerve constrictions were found in DW-MRN, and 29 nerve constrictions were found in US.

Diffusion-weighted MRN is a noninvasive and helpful diagnostic for hourglass-like constriction of the upper limb nerve.

Neuralgic amyotrophy (NA) is markedly underdiagnosed in clinical practice, and its actual incidence rate is about 1 per 1000 per year. In the current article, we provide an overview of essential information about NA, including the etiology, clinical manifestations, diagnostic investigations, differential diagnosis, treatment, and prognosis. The causes of NA are multifactorial and include immunological, mechanical, or genetic factors. Typical clinical findings are a sudden onset of pain in the shoulder region, followed by patchy flaccid paralysis of muscles in the shoulder and/or arm. A diagnosis of NA is based on a patient's clinical history and physical examination. Gadolinium-enhanced magnetic resonance imaging and high-resolution magnetic resonance neurography are useful for confirming the diagnosis and choosing the appropriate treatment. However, before a diagnosis of NA is confirmed, other disorders with similar symptoms, such as cervical radiculopathy or rotator cuff tear, need to be ruled out. The prognosis of NA depends on the degree of axonal damage. In conclusion, many patients with motor weakness and pain are encountered in clinical practice, and some of these patients will exhibit NA. It is important that clinicians understand the key features of this disorder to avoid misdiagnosis.

Nerve ultrasound is a fairly new non-invasive method to visualise peripheral nerves and to detect peripheral nerve lesions. This technique can depict nerve compression syndromes and their aetiologies as well as fascicular torsions. It is also suitable for sonographically guided nerve interventions and for intraoperative navigation. The main advantage of nerve ultrasound is its capability for early diagnosis of severe traumatic nerve lesions that require immediate surgery. Neurologists further use this method to aid the diagnosis of different kinds of polyneuropathies. Within this review we introduce nerve ultrasound to surgeons from a neurological perspective. We focus on different peripheral nerve disorders that might need surgical interventions. Nerve ultrasound will lay the grounds to bring together different expertise in medicine and thus to establish interdisciplinary excellence centres for the understanding, diagnosis and treatment of diseases of the peripheral nervous system.