Focal hole versus screw stimulation to prevent false negative results in detecting pedicle breaches during spinal instrumentation

ObjectiveWe describe a stimulus-evoked EMG approach to minimize false negative results in detecting pedicle breaches during lumbosacral spinal instrumentation.MethodsIn 36 patients receiving 176 lumbosacral pedicle screws, EMG threshold to nerve root activation was determined using a focal probe inserted into the pilot hole at a depth, customized to the individual patients, suitable to position the stimulating tip at the point closest to the tested nerve root. Threshold to screw stimulation was also determined.ResultsMean EMG thresholds in 161 correctly fashioned pedicle instrumentations were 7.5 mA ± 2.46 after focal hole stimulation and 21.8 mA ± 6.8 after screw stimulation. Direct comparison between both thresholds in individual pedicles showed that screw stimulation was always biased by an unpredictable leakage of the stimulating current ranging from 10 to 90%. False negative results were never observed with hole stimulation but this was not true with screw stimulation.ConclusionsFocal hole stimulation, unlike screw stimulation, approaches absolute EMG threshold as shown by the lower normal limit (2.6 mA; p < 0.05) that borders the upper limit of threshold to direct activation of the exposed root.SignificanceThe technique provides an early warning of a possible pedicle breakthrough before insertion of the more harmful, larger and threaded screw.     

A prospective study of high resolution ultrasound in brachial plexopathies – Correlation with electrophysiological measurements

ObjectivesTo evaluate the diagnostic role of ultrasound in brachial plexopathies.MethodsWe included 59 healthy subjects (HS) and 42 patients consecutively referred with clinical suspicion of brachial plexopathy from October 2015 to May 2016. Patients underwent routine electrodiagnostic testing (EDx) as reference standard and a blinded standardised ultrasound examination of the brachial plexus as index test with cross-sectional area (CSA) as the ultrasound parameter of choice.ResultsSeventeen patients were diagnosed by EDx with brachial plexopathy, ten with mononeuropathies, and ten had normal EDx. Five had a cervical radiculopathy. In 11 (64%) out of the 17 patients with EDx diagnosed plexopathy, we found at least one abnormal level on ultrasound. Six (60%) out of ten normal EDx patients had a normal ultrasound examination at all levels. Ultrasound identified the same abnormal level(s) as EDx in eight (73%) of the 11 patients who had both abnormal EDx and ultrasound results. Mean CSA was higher in the plexopathy group compared to HS at the level of the C6 root (p = .022), the middle trunk (p = .027), and the medial cord (p = .003).ConclusionUltrasound examination showed abnormalities in patients with brachial plexopathies in good agreement with EDx.SignificanceUltrasound may be an important supplement to electrodiagnostics in evaluating brachial plexopathies.     

Denervation findings on EMG in amyotrophic lateral sclerosis and correlation with prognostic milestones: Data from a retrospective study

ObjectiveTo verify whether the finding of denervation activity on EMG at the time of diagnosis has a prognostic value in amyotrophic lateral sclerosis (ALS).MethodsWe retrospectively studied all the patients discharged with a diagnosis of ALS between January 2009 and January 2017. 92 patients met the inclusion criteria. We mainly verified three prognostic targets:

• (1)Time to non-invasive ventilation (NIV) or tracheostomy.
• (2)Time to percutaneous endoscopic gastrostomy or parental nutrition.
• (3)Survival.

All EMG examinations were reviewed and a denervation score (DS) was calculated.The association of DS with clinical milestones was analysed, adjusting for disease duration, age , sex, and clinical phenotype.ResultsWe found a significant association between bulbar DS and time to NIV/tracheostomy (HR: 3.34, 95% CI: 1.49 to 7.48, p = 0.002) and with survival (HR 3.633, 95% CI 1.681–7.848, p = 0.001), regardless of the clinical phenotype. Furthermore, we found a significant influence of a general DS on survival (HR: 2.62, 95% CI 1.335–5.160, p = 0.005).ConclusionEMG assessment could be of value not just for ALS diagnosis but also for its intrinsic prognostic value.SignificanceEMG could provide additional information about the rate of progression of ALS as early as the diagnosis is made.     

Basal ganglia and cerebellar circuits have distinct roles in blepharospasm

IntroductionTo identify areas of brain activity associated with involuntary muscle contractions in patients with blepharospasm using functional MRI.Methods15 patients with blepharospasm underwent 8-min resting state scans with spontaneous orbicularis oculi muscle contractions simultaneously recorded using MRI-compatible surface electromyography. Spasm severity and spasm onset/offset were modeled using the amplitude of the electromyography signal (EMG-Amp) and its first temporal derivative (EMG-Onset), respectively, and included in a multiple regression functional MRI analysis using SPM12. Primary outcome was within-group blood-oxygen-level dependent activations that co-varied with EMG-Amp and EMG-Onset following correction for multiple comparisons for an overall cluster corrected p < 0.05. Secondary analyses included testing for correlations between imaging findings and symptom severity, as measured by clinical dystonia rating scales, using an uncorrected voxel-level threshold of p < 0.001.ResultsImaging data from one subject were excluded due to excessive movement. EMG-Amp co-activated within the left sensorimotor cortex and cerebellum, as well as right lingual gyrus and superior temporal gyrus. EMG-Onset co-activated within the left posterior putamen/pallidum and a frontal eye field region in the left superior frontal gyrus. Symptom severity and EMG-Amp significantly co-varied in a small cluster within the left cerebellum.ConclusionOur preliminary findings here suggest that cerebello-cortical circuits in blepharospasm could drive the intensity of eyelid spasms while basal ganglia circuits are associated with the triggering of spasms. This supports the network model for dystonia and identifies specific areas of involvement consistent with known brain regions responsible for control of movement.     

Altered supraspinal motor networks in survivors of poliomyelitis: A cortico-muscular coherence study

ObjectivePoliomyelitis results in changes to the anterior horn cell. The full extent of cortical network changes in the motor physiology of polio survivors has not been established. Our aim was to investigate how focal degeneration of the lower motor neurons (LMN) in infancy/childhood affects motor network connectivity in adult survivors of polio.MethodsSurface electroencephalography (EEG) and electromyography (EMG) were recorded during an isometric pincer grip task in 25 patients and 11 healthy controls. Spectral signal analysis of cortico-muscular (EEG-EMG) coherence (CMC) was used to identify the cortical regions that are functionally synchronous and connected to the periphery during the pincer grip task.ResultsA pattern of CMC was noted in polio survivors that was not present in healthy individuals. Significant CMC in low gamma frequency bands (30–47 Hz) was observed in frontal and parietal regions.ConclusionThese findings imply a differential engagement of cortical networks in polio survivors that extends beyond the motor cortex and suggest a disease-related functional reorganisation of the cortical motor network.SignificanceThis research has implications for other similar LMN conditions, including spinal muscular atrophy (SMA). CMC has potential in future clinical trials as a biomarker of altered function in motor networks in post-polio syndrome, SMA, and other related conditions.     

Differentiation of ulnar neuropathy at the wrist due to ganglion cyst from ulnar neuropathy at the elbow

ObjectiveHere, we aimed to describe the clinical, electrodiagnostic (EDx) and ultrasonographic (US) findings in a series of patients with ulnar neuropathy at the wrist (UNW) due to compression by a ganglion cyst. We also sought features that differentiate UNW from ulnar neuropathy at the elbow (UNE).MethodsWe reviewed electronic medical records of consecutive patients with UNW caused by ganglion cysts. We compared their clinical, EDx and US findings to findings in our previously reported prospective series of UNE patients.ResultsWe identified 10 patients with UNW caused by ganglion cyst compression, who all presented with intrinsic hand muscle weakness and atrophy. Compared to 175 UNE patients they less often complained of paresthesia (60% vs. 98%) and presented less sensory loss in the palm (30% vs. 96%) and little finger (50% vs. 95%). They more often had distal ulnar motor latency recorded from the abductor digiti minimi (ADM) > 3.6 ms (80% vs. 30%), and denervation activity on needle EMG in the first dorsal interosseous (FDI) compared to ADM (100% vs. 60%). Only 20% of our UNW patients had ulnar nerve swelling at the site of compression on US.ConclusionUNW potentially caused by ganglion cyst should be suspected in patients presenting with intrinsic hand muscle atrophy and weakness, particularly in cases with normal sensation, increased distal ulnar motor latency recorded from ADM and more severe neuropathic changes in FDI compared to ADM muscle.     

The diagnostic accuracy of high-resolution ultrasound in screening for carpal tunnel syndrome and grading its severity is moderated by age

ObjectiveTo assess the effect of age on the accuracy of high-resolution ultrasound (HRUS) in the diagnosis and grading of carpal tunnel syndrome (CTS).MethodsPatients with symptoms and signs of CTS (N = 527 wrists) were evaluated using electrodiagnostic studies (EDx) for CTS diagnosis and grading. Median nerve cross-sectional areas at carpal tunnel inlet (CSA) and at forearm level were measured by HRUS and the ratio of these values was calculated (WFR). Healthy controls underwent identical testing (N = 122 wrists). HRUS accuracy was assessed against the EDx standard by Receiver Operator Characteristic (ROC) curve analysis.ResultsIn patients >65 y with moderate and severe CTS, disease-related increases in CSA and WFR were negatively correlated with increasing age. Subjects were grouped by age into younger (<65 y) and older (≥65 y). The c-statistics for CSA and WFR respectively were: For CTS diagnosis, younger group: 0.94 and 0.96 (excellent); older group: 0.85 and 0.86 (satisfactory). For CTS grading, younger group: differentiating mild CTS from controls: 0.90 and 0.92 (excellent); mild from moderate: 0.79 and 0.74 (satisfactory); moderate from severe: 0.82 and 0.78 (satisfactory). For CTS grading, older group: differentiating mild CTS from controls: 0.83 and 0.83 (satisfactory); mild from moderate: 0.53 and 0.61 (poor); moderate from severe: 0.65 and 0.53 (poor).ConclusionsFor subjects aged <65 y, HRUS accuracy is excellent in CTS diagnosis and satisfactory in grading. For older subjects, accuracy is satisfactory in diagnosis but not in grading.SignificanceHRUS for CTS has diagnostic limitations selectively in older individuals.