Eman A. Tawfik

Neuromuscular Ultrasound of Cranial Nerves

Ultrasound of cranial nerves is a novel subdomain of neuromuscular ultrasound (NMUS) which may provide additional value in the assessment of cranial nerves in different neuromuscular disorders. Whilst NMUS of peripheral nerves has been studied, NMUS of cranial nerves is considered in its initial stage of research, thus, there is a need to summarize the research results achieved to date. Detailed scanning protocols, which assist in mastery of the techniques, are briefly mentioned in the few reference textbooks available in the field. This review article focuses on ultrasound scanning techniques of the 4 accessible cranial nerves: optic, facial, vagus and spinal accessory nerves. The relevant literatures and potential future applications are discussed.

A PILOT STUDY OF DIAGNOSTIC NEUROMUSCULAR ULTRASOUND IN BELL'S PALSY

Neuromuscular ultrasound of the cranial nerves is an emerging field which may help in the assessment of cranial neuropathies. The aim of this study was to evaluate the role of neuromuscular ultrasound in Bells palsy. A second objective was to assess the possibility of any associated vagus nerve abnormality.

Diagnostic Ultrasound of the Vagus Nerve in Patients with Diabetes

Autonomic neuropathy is a serious and common complication of diabetes mellitus. The vagus nerve is the longest autonomic nerve, and may be affected in diabetes as a part of generalized neuropathy. Our objective was to assess for possible sonographic changes of the vagus nerve in diabetic patients.

Proposed Sonographic Criteria for the Diagnosis of Idiopathic Tarsal Tunnel Syndrome.

OBJECTIVE To propose new sonographic criteria for the diagnosis of idiopathic tarsal tunnel syndrome (TTS). DESIGN Prospective case-control study. SETTING Academic referral center. PARTICIPANTS Adult healthy volunteers (n=17) and adult patients (n=14) with electrodiagnostically proven idiopathic TTS (mean age, 43.4±8.7y; height, 161.4±7.0cm; weight, 90.6±13.9kg) (N=31). The exclusion criteria were patients with diabetes, neurological disorders, associated ankle and/or foot disorders, electrodiagnostic evidence of a widespread lesion, or feet that were electrophysiologically negative for TTS or with structural abnormalities detected via ultrasound imaging. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Tibial nerve CSA at the proximal tarsal tunnel, tibial nerve CSA within the tunnel, within tunnel-to-proximal tunnel CSA ratio. RESULTS There was a significant difference in the within tunnel CSA and within tunnel-to-proximal tunnel CSA ratio between the TTS group and controls (P=.002 and P=.001, respectively). The optimum cutoff value was 19mm(2) for the within tunnel CSA and 1 for the within tunnel-to-proximal tunnel CSA ratio. Sensitivities were 61% and 74%, respectively. CONCLUSIONS The within tunnel-to-proximal tunnel CSA ratio and the within tunnel CSA are the most accurate sonographic parameters and can be helpful in the assessment of idiopathic TTS.

Sonographic characteristics of the facial nerve in healthy volunteers.

Introduction: Peripheral nerve ultrasound has become an effective imaging technique. However, imaging of cranial nerves, especially in healthy volunteers, has received minimal attention. The objectives of this study were to describe the sonographic characteristics of the facial nerve and to establish average values of its diameter. Methods: The extra‐cranial part of the facial nerve was scanned bilaterally along its longitudinal axis inside the parotid gland using a 13‐MHz probe in 50 healthy adults. The diameter was measured at the nerves thickest region. Results: The facial nerve appeared as a thin, tubular, hypoechoic structure inside the parotid gland. The mean facial nerve diameter was 0.5 ± 0.1 mm, and the mean side‐to‐side difference in diameter was 0.1 ± 0.1 mm. Conclusions: The average facial nerve diameter values may provide help with identification of nerve abnormalities using ultrasound. Muscle Nerve 52: 767–771, 2015

Vagus nerve ultrasound in a patient with amyotrophic lateral sclerosis.

High-resolution ultrasound has become a valuable diagnostic tool in neuromuscular disorders. For many years, it has been utilized to evaluate entrapment neuropathies, but researchers have recently begun to investigate its diagnostic role in generalized neuromuscular diseases. The initial results regarding amyotrophic lateral sclerosis (ALS) are promising and suggest a potential role for ultrasound to identify disease biomarkers. Studies have focused so far on peripheral nerve and muscle ultrasound, and none have addressed cranial nerve ultrasonography in ALS. I report the use of ultrasonography to evaluate the vagus nerve in an ALS patient with mild bulbar symptoms. The study was approved by the local ethics committee, and informed consent was obtained from the patient. A 46-year-old man was referred to the electromyography laboratory for evaluation of a 1.5-year history of progressive weakness of the upper and lower limbs. He reported bulbar symptoms in the form of occasional choking, difficulty swallowing, and a harsh voice. He did not have sensory symptoms or bladder or bowel dysfunction. Cranial nerve examination yielded normal results. The thenar, hypothenar, and intrinsic hand and foot muscles were wasted on both sides. The lower limb muscles were mildly hypertonic, and muscle weakness was more evident distally in the upper and lower extremities. The tendon stretch reflexes of the lower limbs were exaggerated, and extensor plantar responses were noted on both sides. Sensory examination was normal. Motor conduction studies revealed low compound muscle action potential amplitudes in the median, ulnar, and tibial nerves on both sides. The distal motor latencies and conduction velocities were within normal ranges, and there was no evidence of focal conduction block. Sensory nerve conduction studies were normal. Needle electromyography revealed fibrillation potentials, positive sharp waves, and enlarged, polyphasic motor unit action potentials distributed across multiple myotomes. Fasciculation potentials were evident in the biceps brachii and triceps muscles. Fibrillation potentials were also detected in the thoracic paraspinal and sternocleidomastoid muscles. Based on the clinical and electrodiagnostic findings, the patient was diagnosed with clinically probable laboratory-supported ALS according to the revised El Escorial criteria. The vagus nerve was scanned bilaterally using an ultrasound system (Logiq P5; GE Healthcare, New York) and a 13-MHZ linear-array transducer. The transducer was positioned transversely in the lateral neck, and the nerve was identified inside the carotid sheath posterior to the internal jugular vein and carotid artery. The crosssectional area (CSA) was measured by tracing the nerve along the inner aspect of the hyperechoic rim. The vagus nerve CSA was 1 mm on both sides (Fig. 1), which was much smaller than the previously reported reference values obtained from healthy volunteers (means of 5 mm and 5.5 mm). This finding suggests there is vagus nerve atrophy in ALS, and it may reflect a type of degeneration that precedes the occurrence of overt bulbar manifestations. If the observed vagus nerve atrophy is further validated in a large-scale study, it may help establish sonographic criteria for diagnosis of ALS in conjunction with peripheral nerve and muscle ultrasound.

The second lumbrical-interossei latency difference in carpal tunnel syndrome: Is it a mandatory or a dispensable test?

Abstract Objective To assess the value of the 2L-INT latency difference in the electrodiagnosis of the carpal tunnel syndrome (CTS) and evaluate its sensitivity in comparison to other routine median motor and sensory studies. Methods The study was conducted on 100 hands with symptoms and signs suggestive of CTS and 100 non-CTS hands as the control group. All were subjected to routine median motor nerve conduction study with stimulation at midpalm, wrist and elbow, median-versus-radial sensory comparison study and Second lumbrical-versus-interosseus (2L-INT) motor comparison study. Results The results showed that the most sensitive tests were the median-radial sensory test and the 2LINT test and that both were correlated suggesting that the motor fibers of the median nerve can be compressed as early as sensory fibers. Conclusion The 2L-INT test is as sensitive and important as the median-radial sensory test. Significance We recommend the routine use of the 2L-INT test in clinically suspected cases of CTS especially in cases where routine median motor studies are normal together with the median-radial sensory test even if the sensory studies are normal.

Value of electrophysiological testing in unilateral facial palsy

Objective The aim of this study was to assess the value of facial nerve temporal recording in the diagnosis and prognosis of facial nerve palsy. Patients and methods The study was conducted on 42 patients with acute unilateral Bell’s palsy (patients’ group) and 43 healthy volunteers who served as a control group. All patients and controls were subjected to clinical examination in the form of history taking and full general and neurological examinations, clinical scoring system using House–Brackmann facial nerve grading system (performed for the patients’ group only), electrophysiological assessment, which included electroneuronography (ENoG) and facial nerve temporal recording. Results The amplitude of the facial nerve temporal recording was significantly lower in the patients’ group compared with that in the control group, and there was statistically significant increase of the amplitude of facial nerve temporal recording, regaining its normal triphasic waves; as regards correlation study between the percent of degeneration of ENoG and the amplitude of the diseased facial temporal recording, there was positive correlation between them, and it was not reaching the level of statistical significance. Conclusion Facial nerve temporal recording detects the degenerative changes that occur in the intratemporal segment of the facial nerve; hence, it should be considered as a complementary tool for the ENoG test for early diagnosis and follow-up of Bell’s palsy.

Indications for neuromuscular ultrasound: Expert opinion and review of the literature

Over the last two decades, dozens of applications have emerged for ultrasonography in neuromuscular disorders. We wanted to measure its impact on practice in laboratories where the technique is in frequent use. After identifying experts in neuromuscular ultrasound and electrodiagnosis, we assessed their use of ultrasonography for different indications and their expectations for its future evolution. We then identified the earliest papers to provide convincing evidence of the utility of ultrasound for particular indications and analyzed the relationship of their date of publication with expert usage. We found that experts use ultrasonography often for inflammatory, hereditary, traumatic, compressive and neoplastic neuropathies, and somewhat less often for neuronopathies and myopathies. Usage significantly correlated with the timing of key publications in the field. We review these findings and the extensive evidence supporting the value of neuromuscular ultrasound. Advancement of the field of clinical neurophysiology depends on widespread translation of these findings.

Re: Comments on “Neuromuscular Ultrasonography of Cranial Nerves”: The Authors Respond

Dear Editor, We thank Tenuta et al.1 for their interest in our review article, and we appreciate their input and clarifications. We generally agree with the points they have raised. We agree there is no strong evidence for a possible thermal or mechanical effect on the eye using B-mode scans and that the risk is associated more with color Doppler scans. We clarified this when we stated in the review article that color flow and power Doppler imaging are associated with significant increases in the insonation energy during ultrasonography, which results in the eye being vulnerable to the heat generated by the sound waves in these two modes. We stressed this point because safety is critical and novices might want to add the color flow mode indiscriminately when imaging the eye. The Food and Drug Administration recommends that health-care providers consider ways to minimize exposure while maintaining the diagnostic quality when using ultrasound. As with all other imaging modalities, the principle of as low as reasonably achievable (ALARA) should be practiced by health-care providers. Using a closed-eye technique in scanning is encouraged in order to avoid direct contact with the eye structures and cornea, which may cause abrasion. It is also the most common technique described in the literature.2-5 We agree that maintaining the gaze at the midline is near impossible. The 30° test is of interest, and we thank Tenuta et al.1 for describing the technique and the value of the test.