Adeniyi A. Borire

Sonographic differences in carpal tunnel syndrome with normal and abnormal nerve conduction studies.

We evaluated the differences in sonographic parameters in carpal tunnel syndrome (CTS) patients with normal and mildly abnormal nerve conduction studies (NCS). This was a prospective cross-sectional study. We assessed 169 wrists (101 patients) with a clinical diagnosis of carpal tunnel syndrome (CTS), as well as 20 healthy controls (40 wrists). 49 wrists were classified as mild NCS-positive and 38 as NCS-negative based on our laboratory NCS normal values. The cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet and mid-forearm were measured and the wrist-to-forearm ratio (WFR) was calculated. 26% of the NCS-negative group had abnormal CSA. The CSA and WFR also differed significantly between the two groups. There was significant correlation between the sonographic and electrophysiologic variables. Ultrasound was diagnostic for CTS in a third of the NCS-negative wrists. Ultrasound may be useful in clinical CTS patients with normal or borderline NCS.

Utility of maximum perfusion intensity as an ultrasonographic marker of intraneural blood flow.

We quantified intraneural blood flow (INBF) using perfusion measurement software (PixelFlux), and compared it with the qualitative method of counting blood vessels (vessel score) in a cohort of carpal tunnel syndrome (CTS) patients. Methods: Forty‐seven patients (67 wrists) with a clinical and electrophysiological diagnosis of CTS, and 20 healthy controls (40 wrists) were enrolled. Median nerve ultrasound (US) was performed at the carpal tunnel inlet to measure the cross‐sectional area (CSA) and vessel score. Power Doppler sonograms from nerves with detectable INBF were processed with PixelFlux to obtain the maximum perfusion intensity (MPI). Results: Forty‐nine percent of CTS patients had detectable INBF compared with none in the control group (P < 0.0001). MPI correlated significantly with vessel score (r = 0.945, P < 0.0001), CSA (r = 0.613, P < 0.0001), and electrophysiological severity (r = 0.440, P < 0.0001). MPI had higher intra‐ or interobserver reliability compared with vessel score (0.95 vs. 0.47). Conclusion: MPI is a better method for quantification of INBF. Muscle Nerve, 2016 Muscle Nerve 55: 77–83, 2017

Haemodialysis alters peripheral nerve morphology in end-stage kidney disease

OBJECTIVE We explored the nerve ultrasound (US) characteristics of 15 patients with end-stage kidney disease (ESKD) and correlated these findings with clinical severity and electrophysiological parameters of neuropathy. METHODS 15 ESKD patients on thrice-weekly high-flux haemodialysis and 15 healthy controls were enrolled. Sonographic and electrophysiologic studies were conducted before and after a single session of haemodialysis. Serial measurements of median nerve cross-sectional area (CSA) and hypoechoic fraction (HF) were performed at the same non-entrapment site in the mid-forearm. Neuropathy severity was quantified using the total neuropathy score (TNS). RESULTS 86.7% of the ESKD cohort had neuropathy (TNS>1). ESKD patients had significantly higher baseline CSA (8.9±1.2mm2 vs 7.5±1.0mm2, p<0.05) and HF (56.0±1.0% vs 54.0±1.1%, p<0.05) compared with the control group. The CSA correlated significantly with TNS (r=0.826; p<0.0001) and other electrophysiological parameters. There was a reduction in both the CSA (8.3±1.4mm2; p<0.01) and HF (55.0±1.6%; p<0.05) after a single session of HD. A significant relationship was also found between the change in CSA and change in serum K+ after dialysis (r=0.782, p<0.01). CONCLUSIONS This study shows that peripheral nerves in ESKD patients are larger and more hypoechoic and that these morphological abnormalities may be reversed by dialysis. SIGNIFICANCE US may be useful as an early marker of neuropathy in ESKD.

cVEMP morphology changes with recording electrode position, but single motor unit activity remains constant

Cervical vestibular evoked myogenic potentials (cVEMPs) recorded over the lower quarter of the sternocleidomastoid (SCM) muscle in normal subjects may have opposite polarity to those recorded over the midpoint. It has thus been suggested that vestibular projections to the lower part of SCM might be excitatory rather than inhibitory. We tested the hypothesis that the SCM muscle receives both inhibitory and excitatory vestibular inputs. We recorded cVEMPs in 10 normal subjects with surface electrodes placed at multiple sites along the anterior (sternal) component of the SCM muscle. We compared several reference sites: sternum, ipsilateral and contralateral earlobes, and contralateral wrist. In five subjects, single motor unit responses were recorded at the upper, middle, and lower parts of the SCM muscle using concentric needle electrodes. The surface cVEMP had the typical positive-negative polarity at the midpoint of the SCM muscle. In all subjects, as the recording electrode was moved toward each insertion point, p13 amplitude became smaller and p13 latency increased, then the polarity inverted to a negative-positive waveform (n1-p1). Changing the reference site did not affect reflex polarity. There was a significant short-latency change in activity in 61/63 single motor units, and in each case this was a decrease or gap in firing, indicating an inhibitory reflex. Single motor unit recordings showed that the reflex was inhibitory along the entire SCM muscle. The cVEMP surface waveform inversion near the mastoid and sternal insertion points likely reflects volume conduction of the potential occurring with increasing distance from the motor point.

Tonsillar Herniation After Lumbar Puncture in Idiopathic Intracranial Hypertension.

A 30-year-old woman with coexisting renal tubular acidosis and idiopathic intracranial hypertension (IIH), treated with acetazolamide, experienced coning (cerebellar tonsillar herniation) after a lumbar puncture (LP). Brain magnetic resonance imaging at initial diagnosis of IIH showed minor tonsillar descent and computed tomographic venography revealed hypoplasia of the left transverse sinus. The patient previously had three uneventful LPs, all of which showed high opening pressures and normal cerebrospinal fluid composition. In retrospect, it was noted that her serum bicarbonate had fallen to 9 mmol/L (normal: 22-28 mm/L) 1 week before the LP. We hypothesize that the combination of cerebral edema (due to worsening metabolic acidosis), poor venous drainage, and preexisting minor tonsillar descent contributed to her post-LP coning.

Effects of haemodialysis on intraneural blood flow in end-stage kidney disease

Introduction: We quantified intraneural blood flow (INBF) in 18 patients with end‐stage kidney disease (ESKD) and examined its relationship with nerve size, neuropathy severity, and nerve excitability parameters. Methods: Sonographic measurements of the median nerve were performed at the same site before and after hemodialysis. INBF was quantified by analyzing power Doppler sonograms to obtain the vessel score (VSc) and maximum perfusion intensity (MPI). Corresponding median motor nerve excitability studies were performed. Neuropathy severity was assessed using Total Neuropathy Score. Results: A total of 39% of ESKD patients had detectable INBF compared with none in the control group (P < 0.0001). Patients with detectable INBF had larger nerves and more severe neuropathy (P < 0.01). INBF parameters were significantly reduced after a session of dialysis (VSc: P < 0.01; MPI: P < 0.01). A significant relationship was found between interdialytic change in INBF and changes in nerve excitability. Conclusions: Increased INBF is a potential marker for neuropathy severity in ESKD patients. Muscle Nerve 57: 287–293, 2018

The provision of written information and its effect on levels of pain and anxiety during electrodiagnostic studies: A randomised controlled trial

Objective The provision of written information is a low-cost and readily available intervention that has been found to reduce pain and anxiety in a variety of clinical settings. The current study was undertaken to determine if information provision may improve patients’ experience during conventional electrodiagnostic studies. Methods 128 participants were recruited from a tertiary teaching hospital who were referred for electrodiagnostic studies. They were randomized into 2 groups where the intervention group was provided with written information about the electrodiagnostic testing. Patients were invited to complete a questionnaire that included pain and anxiety using a visual analogue scale (VAS) following the testing. All participants underwent nerve conduction studies (NCS) whilst a subset also underwent subsequent needle electromyography (EMG). Results Those who received information had a statistically significant lower perception of anxiety during NCS, whilst only females who received information had a statistically significant lower perception of pain to both NCS and EMG. Conclusions The provision of written information can reduce the degree of pain and anxiety experienced during electrodiagnostic testing. Significance Improving patient comfort and tolerability during electrodiagnostic testing may have practical implications towards more reliable and accurate results obtained from such investigations that may in turn improve patient diagnosis and management.

Correlation between markers of peripheral nerve function and structure in type 1 diabetes

Clinical and experimental studies in patients with type 1 and type 2 diabetes have demonstrated changes in ion channel function and nerve structure. In this study, we investigated the relationship between axonal dysfunction and morphological change in diabetic polyneuropathy by using neuromuscular ultrasound and nerve excitability techniques. We also explored possible differences in this relationship between type 1 and type 2 diabetes.

Association between peripheral nerve function and structure in human diabetic nerves

Objectives We explored the nerve ultrasound (US) characteristics of diabetic patients and correlated these findings with clinical severity and electrophysiological parameters. Methods One-hundred and twenty diabetic patients (90 type 2; 30 type 1) underwent comprehensive neurologic assessment, nerve conduction studies, US and excitability assessment. Neuropathy severity was assessed using Total Neuropathy Score (TNS). Median nerve sonographic assessment was performed at a non-entrapment site, to obtain the cross-sectional area (CSA) and vessel score. Power Doppler sonograms from nerves with detectable intraneural blood flow (INBF) were processed with PixelFlux to obtain the maximum perfusion intensity (MPI). Corresponding median motor excitability studies were performed. Results Median nerve CSA was significantly higher in diabetic patients compared with controls (8.03±0.21 mm2 vs 7.1±0.4 mm2, p<0.05). 58% of the diabetes cohort had neuropathy (TNS>1), with larger nerves compared with non-neuropathic subjects (8.64±0.33 mm2 vs 7.33±0.20 mm2, p<0.05). Nerve size increased with worsening neuropathy severity, demonstrated by the correlation between CSA and TNS (r=0.496; p<0.0001). 20.3% of diabetic patients had detectable INBF compared with none in the control group (p<0.0001). Patients with detectable INBF had larger nerves (9.56±0.64 mm2 vs 7.64±0.18 mm2, p<0.05), and more severe neuropathy (p<0.05). A strong relationship was found between CSA and INBF (vessel score: r=0.475, p<0.01; MPI: r=403, p<0.01). Subgroup analysis revealed that CSA correlated significantly with excitability parameters in type 1 patients (TEd10-20 ms: r=−0.752, p<0.01; TEd40-60ms: r=−0.845, p<0.001; TEd90–100ms: r=−0.891, p<0.001; refractoriness: r=0.664, p<0.01). In contrast, no correlation was found between CSA and excitability parameters in type 2 patients. Conclusions This study demonstrates significant nerve enlargement in diabetic patients, which correlates well with neuropathy severity, and may potentially be a biomarker for early diagnosis. Detectable INBF was predominantly seen in patients with moderate to severe neuropathy, suggesting that this may be a marker of severity or axonal loss. The study also provides further evidence that different pathophysiological mechanisms lead to the development of neuropathy in type 1 and type 2 diabetes.

13. Comparison of digits 2 and 3 sensory studies in patients with carpal tunnel syndrome

Introduction According to AANEM guidelines, an initial step in the electrodiagnostic study for carpal tunnel syndrome (CTS) is the recording of median sensory response across the wrist. Although any median nerve innervated digit can be studied, digit 2 is most common. Objective The current prospective study was undertaken to determine differences between median nerve sensory parameters following stimulation of digit 2 and 3 in patients presenting with clinical CTS. Methods We prospectively studied 211 wrists in 158 patients with clinically definite CTS defined as nocturnal and/or activity-related sensory symptoms, sensory deficits in the median nerve distribution, or weakness and/or atrophy of median-innervated thenar muscles. Electrophysiological studies were conducted using standard techniques based on the AANEM practice parameters. Specifically, orthodromic sensory studies were performed following stimulation of both digit 2 and 3. Comparison sensory studies with the radial nerve were performed with stimulation at digit 1. Median motor studies were also performed. A cohort of normal patients were also recruited and studied. Results Sensory conduction velocity (SCV) following digit 3 stimulation (32.3 ± 14.5m/s) was significantly slower ( P 0.001) when compared to digit 2 (35.1 ± 14.1m/s) in all severity groups, although the difference was most pronounced in patients with mild compared to those with severe CTS ( p =0.005). 5% of the total cohort had normal digit 2 SCV, but abnormal digit 3 SCV. In our cohort of normal wrists, there was no significant difference between digits 2 and 3 SCV and sensory amplitude. Conclusion Orthodromic median nerve sensory studies following digit 3 stimulation are significantly more abnormal compared to digit 2 stimulation in patients with CTS, and may be more sensitive for the diagnosis of CTS, particularly in mild cases.