Peripheral nerve injection injury with antiemetic agents

Sciatic nerve injury following analgesic drug injection in rats: A histopathological examination

OBJECTIVE:

Sciatic nerve neuropathy can be observed following intramuscular gluteal injections. The histopathological examination of sciatic nerve damage following intramuscular injection in the gluteal region for acute pain treatment is not feasible in humans due to the inability to dissect and examine the nerve tissue. To overcome this issue, we used a rat model for demonstrating damage to the sciatic nerve tissue after the application of commonly used drug injections.

METHODS:

We investigated possible damage following the intramuscular injection of diclofenac, lornoxicam, morphine, and pethidine in a rat model based on histopathological characteristics such as myelin degeneration, axon degeneration, epineurium degeneration, fibrosis, epineurium thickening, perineurium thickening, lymphocyte infiltration, vacuolization, and edema.

RESULTS:

All the analgesic drugs used in our study induced histopathological changes in the sciatic nerve. Anti-S100 positivity, showing nerve damage, was found to be the lowest in the group treated with diclofenac. Neurotoxic effects of diclofenac on the sciatic nerve were greater than those of the other drugs used in the study. Lornoxicam induced the least histopathological changes in the nerve.

CONCLUSION:

Diclofenac induced severe nerve damage not only after direct injection in the sciatic nerve but also after injection in the area around the nerve. Thus, we recommend restricting the use of intramuscular gluteal injections of diclofenac. Intramuscular use of morphine and pethidine should also be overviewed.

Iatrogenic Axillary Neuropathy After Intramuscular Injection of the Deltoid Muscle

A previously healthy 26-yr-old male presented for an electrodiagnostic evaluation with complaints of significant right deltoid muscle atrophy and shoulder abduction weakness after receiving an intramuscular (IM) deltoid injection of an antiemetic 4 wk earlier. Electrodiagnostic evaluation confirmed an acute axillary neuropathy. We hypothesize that direct mechanical trauma to the anterior branch of the axillary nerve resulted in axillary mononeuropathy with axonal loss, although chemically induced nerve injury cannot be excluded. Injections in and about the shoulder complex are performed routinely for the purposes of vaccination, IM medication administration, deltoid trigger-point injections, and intra-articular and bursal steroid injections. Although such injections are considered routine office procedures, there is increased risk of neurovascular injury if they are performed incorrectly. The purpose of this brief report is to make practitioners aware of the potential for axillary neuropathy with such procedures, to review the salient anatomy, and to propose a potential guideline for clinical practice to minimize iatrogenic axillary neuropathy.

Neurologic and histologic outcome after intraneural injections of lidocaine in canine sciatic nerves

BACKGROUND

Inadvertent intraneural injection of local anesthetics may result in neurologic injury. We hypothesized that an intraneural injection may be associated with higher injection pressures and an increase in the risk of neurologic injury.

METHODS

The study was conducted in accordance with the principles of laboratory animal care, and was approved by the Laboratory Animal Care and Use Committee. Fifteen dogs of mixed breed (16-21 kg) were studied. After general endotracheal anesthesia, the sciatic nerves (n= 30) were exposed bilaterally. Under direct vision, a 25-gauge, long-beveled needle (30 degrees) was placed either epineurally (n= 10) or intraneurally (n= 20), and 4 ml of preservative-free lidocaine 20 mg/ml was injected using an automated infusion pump (4 ml/min). Injection pressure data were acquired using an in-line manometer coupled to a computer via an analog-to-digital conversion board. After injection, the animals were awakened and subjected to serial neurologic examinations. One week later, the dogs were killed, the sciatic nerves excised and histologic examination was performed by pathologists blind to the purpose of the study.

RESULTS

All perineural injections resulted in low pressures (< or = 5 psi). In contrast, eight of 20 intraneural injections resulted in high pressures (20-38 psi) at the beginning of the injection. Twelve intraneural injections, however, resulted in pressures of less than 12 psi. Neurologic function returned to baseline within 3 h after perineural injections and within 24 h after intraneural injections, when the measured injection pressures were less than 12 psi. Neurologic deficits persisted throughout the study period after all eight intraneural injections that resulted in high injection pressures. Histologic examination of the affected nerves revealed fascicular axonolysis and cellular infiltration.

CONCLUSIONS

The data in our canine model of intraneural injection suggest that intraneural injections do not always lead to nerve injury. High injection pressures during intraneural injection may be indicative of intrafascicular injection and may predict the development of neurologic injury.

Safe injection of cultured schwann cells into peripheral nerve allografts

The effects of cultured host Schwann cells on axonal regeneration in peripheral nerve allografts were studied. Fischer rats served as recipient animals and Buffalo rats provided nerve allografts. Animals were randomized into 9 groups. Rats receiving tibial nerve isografts were left untreated (group I), or injected with isogeneic Fischer Schwann cells (group II) or placebo suspension (group III). Allografts obtained from Buffalo rats were left untreated (group IV), or received isogeneic Fischer Schwann cells (group V), 2 mg/kg Cyclosporin A and Fischer Schwann cells (group VI), 5 mg/kg Cyclosporin A (group VII), or 5 mg/kg Cyclosporin A with Schwann cells (group VIII). No Schwann cell tumors were identified 4 or 8 weeks postoperatively. Group IX animals, harvested 3 days postoperatively, demonstrated no evidence of injection injury. Schwann cells modestly improved axonal regeneration in both isografts and allografts and may have a clinical role in the treatment of peripheral nerve allografts.