Daniel A. Lazar

High-resolution Magnetic Resonance Imaging Is a Noninvasive Method of Observing Injury and Recovery in the Peripheral Nervous System

OBJECTIVENoninvasive observation of degenerating and regenerating peripheral nerves could improve the diagnosis and treatment of nerve injuries. We constructed a novel phased-array radiofrequency coil to permit magnetic resonance imaging (MRI) observation of the sciatic nerve and its target muscles in rats after injury. METHODSAdult male Lewis rats underwent either crushing (n = 18) or cutting and capping (n = 17) of their right sciatic nerves and then underwent serial MRI. Serial gait track analysis was performed to assess behavioral recovery. Animals from both groups were killed at several time points for histological evaluation of the nerves, with axon counting. RESULTSCrushed sciatic nerves demonstrated increased T2-weighted signals, followed by signal normalization as axonal regeneration and behavioral recovery occurred. Cut sciatic nerves prevented from regenerating displayed a prolonged phase of increased signal intensity. Acutely denervated muscles exhibited hyperintense T2-weighted signals, which normalized with reinnervation and behavioral recovery. Chronically denervated muscles demonstrated persistently increased T2-weighted signals and atrophy. CONCLUSIONIn this study, we demonstrated the ability of MRI to noninvasively monitor injury and recovery in the peripheral nervous system, by demonstrating changes in nerve and muscle that correlated with histological and behavioral evidence of axonal degeneration and regeneration. This study demonstrates the potential of MRI to distinguish traumatic peripheral nerve injuries that recover through axonal regeneration (i.e., axonotmetic grade) from those that do not and therefore require surgical repair (i.e., neurotmetic grade). This diagnostic modality could improve treatment by providing earlier and more accurate diagnoses of nerve damage, as well as reducing the need for exploratory surgery.

Ultrasound Accelerates Functional Recovery after Peripheral Nerve Damage

OBJECTIVE Axonal injury in the peripheral nervous system is common, and often it is associated with severe long-term personal and societal costs. The objective of this study is to use an animal model to demonstrate that transcutaneous ultrasound can accelerate recovery from an axonotmetic injury. METHODS The sciatic nerve of adult male Lewis rats was crushed in the right midthigh to cause complete distal degeneration of axons yet maintain continuity of the nerve. Beginning 3 days after surgery, various transcutaneous ultrasound treatments or sham treatments were applied 3 days per week for 30 days to the crush site of rats that were randomly assigned to two groups. In the preliminary experiments, there were three animals in each ultrasound group and two control animals. In the final experiment, there were 22 animals in the ultrasound group and 20 animals in the control group. Recovery was assessed by use of a toe spread assay to quantify a return to normal foot function in the injured leg. Equipment included a hand-held transducer that emitted continuous-wave ultrasound. The most successful ultrasound protocol had a spatial peak, time-averaged intensity of 0.25 W/cm2 operated at 2.25 MHz for 1 minute per application. RESULTS Rats subjected to the most successful ultrasound protocol showed a statistically significant acceleration of foot function recovery starting 14 days after injury versus 18 days for the control group. Full recovery by the ultrasound group occurred before full recovery by the control group. CONCLUSION Transcutaneous ultrasound applied to an animal model of axonotmetic injury accelerated recovery. Future studies should focus on identification of the mechanism(s) by which ultrasound creates this effect, as a prelude to optimization of the protocol, demonstration of its safety, and its eventual application to humans.

Hemorrhagic Complications of Intracranial Pressure Monitors in Children

Intracranial pressure (ICP) monitoring plays a valuable role in the management of head injuries and other causes of raised ICP in the pediatric population. The purpose of this study was to investigate the incidence of hemorrhage after ICP monitor insertion, and to classify these complications in a clinically relevant manner. Hospital charts of 431 children (ages 0–16 years) admitted to a level I trauma center over a 2-year period were reviewed and 112 patients (134 insertions) who underwent intraparenchymal ICP monitoring were identified. The authors reviewed postoperative neuroradiological studies. One hundred and nineteen procedures were carried out without any hemorrhage (grade 0). After 10 insertions, a small punctate hemorrhage or localized subarachnoid hemorrhage occurred (grade 1). Three patients sustained an intracerebral hemorrhage that did not require evacuation or manifest as a new neurological deficit (grade 2). There were no hemorrhagic complications that necessitated evacuation or resulted in a noticeable change in the patient’s clinical condition (grade 3). We propose a new grading system for hemorrhage after ICP monitor insertion. We found a complication rate close to 10% in our pediatric patients. Fortunately, these hemorrhages were clinically silent and no neurosurgical intervention was necessary. However, grade 1 and grade 2 hemorrhages may manifest with a false reading of high ICP, and the long-term consequences of these complications are not known. Of note, only 23% of these complications were reflected in the patients charts, which may explain the low complication rates reported in other studies that did not analyze postoperative neuroradiological studies.

Accurate Intraoperative Localization of Spinal Dural Arteriovenous Fistulae with Embolization Coil: Technical Note

SPINAL DURAL ARTERIOVENOUS fistulae represent a potentially curable cause of a progressive myelopathy and therefore should be treated aggressively by either endovascular or surgical methods. In the surgical treatment of these lesions, intraoperative radiographic localization of the site of the fistula can be problematic. We describe an endovascular technique in which radiopaque microcoils are placed in the major feeding artery(ies) after completion of spinal angiography, which then provides a marker that is easily visualized with intraoperative x-rays, allowing effective localization of the site of the fistula.

Isolated Superior Orbital Fissure Syndrome Resulting From Gunshot Wound to the Head

A 41-year-old man, shot in the face with a handgun, showed left V1 paraesthesia, limited light perception in the left eye, and complete ophthalmoplegia with proptosis and mydriasis. Unenhanced computed tomography (CT) scan showed multiple comminuted fractures of the left orbit, with the bullet lodged near the superior orbital fissure (Fig 1A). Cranial CT angiogram (Fig 1B) and cerebral angiogram (Fig 2) showed dilation of the left superior orbital vein and an isolated segmental 50% narrowing of the internal carotid artery without intrinsic abnormality. Surgical exploration was declined. Despite treatment with high-dose steroids, severe ophthalmoplegia remained, although vision rapidly improved. The complexity of the orbital apex is related to the confluence of crucial neurovascular structures as they transition from the cranium to the orbit and face. The ophthalmic artery and cranial nerves (CN) II, III, IV, V1, and VI transition from the middle cranial fossa to the orbital apex via the superior orbital fissure. Medially, the superior orbital fissure is enclosed by the annulus of Zinn, from which the 4 extraocular recti muscles arise. The infraorbital artery and vein and CN V2 transition via the infraorbital foramen. Superior orbital fissure syndrome (SOFS) reflects injury to neurovascular structures traversing the superior orbital fissure manifest by fixed and dilated pupil (parasympathetic branches of CN III), ptosis and ophthalmoplegia (CN III, IV, VI), proptosis (superior ophthalmic vein), and anesthesia of the forehead and upper eyelid (CN V1) 1,2 and occurs in

Ultrasound accelerates the healing of damaged peripheral nerves invivo

Peripheral nerve injury is a common clinical problem that often debilitates by producing significant motor and sensory deficits, as well as pain and other unpleasant sensations. Recovery is often slow. Patients with proximal injuries that require axons to regenerate over long distances to reach their target muscles or sensory receptors can take up to 2 years to recover function. Moreover, slow recovery can often be incomplete, due to the associated muscle atrophy, decrease in axonal regeneration along the pathway of the degenerating nerve, and decay in the axonal receptivity of the target tissues. In this work, we show that low‐intensity therapeutic ultrasound can accelerate functional recovery in an animal model of a completely crushed peripheral nerve.