Dongqing Zhu

Compound Muscle Action Potential Decrement to Repetitive Nerve Stimulation Between Hirayama Disease and Amyotrophic Lateral Sclerosis.

Purpose: To compare repetitive nerve stimulation (RNS) between Hirayama disease (HD) and amyotrophic lateral sclerosis (ALS). Methods: The 3-Hz RNS test was performed on bilateral abductor pollicis brevis, abductor digiti minimi, middle deltoid, and upper trapezius muscles in 33 HD patients and 37 ALS patients. Results: In HD patients, none of tested muscles showed any abnormal decrements (≥10%). Significant decrements were observed in 73% of the ALS patients, and decrements were more frequently observed in proximal muscles (deltoid: 70.3%; trapezius: 48.6%). Illness duration did not correlate with decrement percentage in either patient group, and there was no relationship between decrement incidence and ALS diagnostic category (P > 0.05). Conclusions: The significantly different RNS results between ALS and HD patients support the application of RNS, especially performing RNS in proximal muscles, as a supplementary test in distinguishing these two diseases, even in the early stages. These results may also imply a difference in underlying pathophysiology between ALS and HD.

Motor unit number estimation in the quantitative assessment of severity and progression of motor unit loss in Hirayama disease

OBJECTIVE To investigate motor unit number estimation (MUNE) as a method to quantitatively evaluate severity and progression of motor unit loss in Hirayama disease (HD). METHODS Multipoint incremental MUNE was performed bilaterally on both abductor digiti minimi and abductor pollicis brevis muscles in 46 patients with HD and 32 controls, along with handgrip strength examination. MUNE was re-evaluated approximately 1year after initial examination in 17 patients with HD. RESULTS The MUNE values were significantly lower in all the tested muscles in the HD group (P<0.05). Despite abnormally low MUNE values, 54.3% (25/46) of patients with HD had normal ipsilateral grip power. There was a significant inverse correlation between MUNE values and disease duration (P<0.05). A longitudinal follow-up MUNE analysis demonstrated slow progression of motor unit loss in patients with HD within approximately 1year (P<0.05), even in patients with an illness duration >4years. CONCLUSIONS A reduction in the functioning motor units was found in patients with HD compared with that in controls, even in the early asymptomatic stages. Moreover, the motor unit loss in HD progresses gradually as the disease advances. SIGNIFICANCE These results have provided evidence for the application of MUNE in estimating the reduction of motor unit in HD and confirming the validity of MUNE for tracking the progression of HD in a clinical setting.

Proximally evoked soleus H‐reflex to S1 nerve root stimulation in sensory neuronopathies (ganglionopathies)

Sensory neuronopathy (SNN) mimics distal sensory axonopathy. The conventional H‐reflex elicited by tibial nerve stimulation (tibial H‐reflex) is usually abnormal in both conditions. We evaluated the proximally evoked soleus H‐reflex in response to S1 nerve root stimulation (S1 foramen H‐reflex) in SNN.

A double determination of central motor conduction time in the assessment of Hirayama disease

OBJECTIVE To investigate central motor conduction time (CMCT) in patients with Hirayama disease (HD) and to analyse the role of motor nerve root lesions in the pathogenesis of HD. METHODS CMCT measured by F-wave (CMCT-F) and by paravertebral magnetic stimulation (CMCT-M) was performed on both abductor pollicis brevis (APB) and abductor digiti minimi (ADM) in 41 HD patients and 22 controls. All patients underwent neck-flexion magnetic resonance imaging evaluation. RESULTS Prolonged CMCT (CMCT-F and/or CMCT-M) was recorded in at least one tested muscle from 7/41 (17.1%) HD patients, and 4 cases presented significant prolonged CMCT-M with normal CMCT-F on the side with significant cervical cord forward-shifting. This asymmetric forward-shifting was identified in 13 HD patients, and forward-shifting on the symptomatic side was more obvious. Compared to the controls (ADM: 0.9±0.3ms; APB: 0.8±0.3ms) and the other 28 HD patients (symptomatic side: ADM: 0.8±0.2ms, APB: 0.8±0.3ms), increased nerve root conduction times were demonstrated in these symptomatic sides (ADM: 1.5±0.7ms; APB: 1.2±0.6ms) (P<0.05). CONCLUSIONS Motor nerve root may be main lesion site in some HD patients, especially on the symptomatic side of patients with asymmetric neck-flexion cervical cord forward-shifting. SIGNIFICANCE Compared to spinal motor neuron lesions, damage to motor nerve root (intra- and/or extra-medullary motor roots) may play an equally important role in the pathogenesis of HD. Abnormally increased forward traction in shorter nerve roots may be the cause for the main damage in motor nerve root.

Altered motor axonal excitability in patients with cervical spondylotic amyotrophy

OBJECTIVE To investigate the changes in motor axonal excitability properties in cervical spondylotic amyotrophy (CSA). METHODS Threshold tracking was used to measure the median motor axons in 21 patients with CSA, 10 patients with cervical spondylotic radiculopathy (CSR) and 16 normal controls. RESULTS Compared with normal controls, patients with distal-type CSA showed increased threshold electrotonus hyperpolarization (TEh [90-100]) and increased superexcitability on the symptomatic side (P < 0.05), which are suggestive of distal motor axonal hyperpolarization, presumably due to motor axonal regeneration. More importantly, compared with normal controls and CSR cases, both distal- and proximal-type CSA cases showed lower accommodation during depolarising currents (reduced S2 accommodation, decreased TEd [undershoot] and/or lower subexcitability) (P < 0.05), indicating that slow K+ conductance may be less active in motor axons in patients with CSA. CONCLUSIONS The present study demonstrated changes in motor axonal excitability in patients with CSA compared with both normal controls and patients with CSR. SIGNIFICANCE Less expression of slow K+ conductance may confer greater instability in membrane potential in CSA, thereby presumably contributing to the increased vulnerability of motor axons in patients with CSA.

CAN anterior cervical fusion procedures prevent the progression of the natural course of Hirayama disease? An ambispective cohort analysis

OBJECTIVE To clarify the effectiveness of anterior cervical fusion (ACF) in the treatment of Hirayama disease (HD). METHODS Sixty-nine HD patients who accepted ACF procedures underwent dynamic F-waves before and soon after operation, and 36 of the 69 patients underwent pre- and postoperative magnetic resonance imaging (MRI). Motor unit number estimation, handgrip strength (HGS) and disabilities of arm, shoulder and hand (DASH) were performed in these 36 HD patients and in the other 24 patients who accepted neither neck-collar support nor operation, and these tests were reassessed about one year after initial test. RESULTS Postoperatively, dynamic F-wave abnormalities were observed in fewer HD cases (2/69 vs. 25/69), and neck-flexion MRI abnormalities decreased significantly (P < 0.05). Compared with motor unit loss in patients who were untreated, follow-up analysis demonstrated no differences in motor unit, HGS or DASH in HD patients who underwent operation (P > 0.05), and mild recovery of motor units was observed in patients with preoperative abnormal dynamic F-waves (P < 0.05). CONCLUSIONS ACF procedures can immediately remove neck-flexion abnormalities and prevent or delay the progression of HD. SIGNIFICANCE ACF procedures may provide effective, reliable and alternative methods for the treatment of HD, especially in HD patients with functional evidence of neck-flexion abnormalities.

T26. Clinical, neurophysiological features of neuropathies induced by abuse of nitrous oxide

Introduction Nitrous Oxide (N 2 O) is a kind of oxidant, which has been used as an inhalation anesthetic agent for pain and surgery. It is usually inhaled from a balloon and it’s known to precipitate vitamin B12 deficiency and may cause neurologic, hematologic and reproductive disorders. Methods Two cases with neuropathies induced by abuse of N 2 O admitted to our hospital were studied. The clinical and neurophysiological data were analyzed. Results Case 1: A 21 years old male patient developed lower limb weakness and numbness in both feet with walking unsteadily, following twice a week inhalation of N 2 O for one month. Neurological examination demonstrated both lower extremities weakness, left more than right, distal more than proximal. Sensory disturbances were found at below the ankles. Ankle reflexes were absent on both sides. Blood routine was normal; folic acid: 7.07 ng/ml, Vitamin B12: 116 pg/ml; CSF analysis and Immune tests were normal, MRI of lumbar and thoracic was normal. EMG showed denervation potentials in both TA and MG muscles; NCS showed the amplitudes of CMAPs of peroneal and tibial nerves were reduced, but MCV and distal latencies were normal. SCS and F waves were within normal ranges. H reflexes were absent bilaterally. He was treated with mecobalamin for 2 weeks and fully recovered. Case 2: A 17 years old female patient developed weakness and paresthesias in both legs and numbness in both hands following intermittent inhalation of N 2 O for 6 months. On examinations the muscle strength of ankle dorsal and planter flexions were 1/5, knee flexions and extensions were 4/5 pin prick sensation was reduced at below knees. Knee and ankle reflexes were absent bilaterally. Blood routine was normal. Vitamin B12 was at subnormal lever. CSF analysis and GM1 and GQ1b tests were normal. NCS showed absent of CMAP of both peroneal and tibial nerves. F waves were absent and sensory nerve conduction studies were normal. H reflexes were absent bilaterally. She was also treated with mecobalamin for one month with substantial clinical improvement. Conclusion The distinctive clinical and neurophysiology pattern of N 2 O induced neuropathies demonstrate an acute, motor severer than sensory, length dependent, axonal polyneuropathy. Its severity is related to the amount of N 2 O abused. The patients improved substantially after vitamin B12 supplement when the patients abstained from further nitrous oxide abuse.

S165. Henneman’s size principle for the motor neurons recruitment of human spinal reflex: Evidences from a study of H reflexes during acute compression/ischemia

Introduction In H reflex studies, H waves are recruited from the reflex-elicited depolarization of the Alpha motor neurons, which follows the Henneman’s size principle that the small motor neurons are responsible for the early portion of the recruitment of the H-reflex. However, there has not been a successful experiment in human with EMG techniques to demonstrate this principle. The goal of this study is to demonstrate that small motor fibers are responsible for the elicitation of the H-reflex in the soleus and flexor carpi radialis (FCR) muscles by blocking the conduction of large motor nerve fibers of the tibial and median nerve using partial ischemia via blood pressure cuff. Methods This prospective study recruited 8 health resident physicians (4 m, 4 F). Electrical stimulation to the tibial nerve at the popliteal fossa, with recording from the soleus and to median nerve at above the elbow with recording from FCR was titrated to elicit both M and H waves, with ratios of amplitudes at 1:1. Compression by a blood pressure cuff was placed at the proximal tibia during tibial nerve stimulations, and at the forearm just distal to the elbow for median nerve stimulation. Stimulations with pulse duration of 1 ms at intervals of 2 s were delivered to the two nerves before, during, and post compression/ischemia. Results In all the subjects tested, during blood pressure cuff inflation, the M-waves of the two muscles consistently demonstrated significant loss of amplitude (or disappeared) with mild increase of latency, while the H-reflex showed no, or very mild amplitude reductions without changes in latency. After blood pressure cuff deflation, the M-waves immediately returned to their previous amplitude and latency patterns. There was a significant dissociation between the changes of M and H waves during acute partial compression/ischemia. Conclusion Acute compression/ischemia instantly causes nerve conduction block of the tibial and median nerves motor fibers and reduces the amplitude of the M waves, but not the H-reflexes. M waves elicited by electrical stimulation recruit large motor fibers first, and are more susceptible to the ischemic blockade applied. By contrast, the H reflex first recruits small motor neurons, with their smaller motor nerve fibers less susceptible to partial acute compression/ischemia. This experiment demonstrates the Henneman’s size principle that the smallest motor units are recruited first during spinal reflexes and volitional muscle contraction. It is also of important significance in the application of motor rehabilitation with therapeutic and functional electrical stimulation of nerves and muscles.

Changes in the soleus H-reflex test and correlations between its results and dynamic magnetic resonance imaging abnormalities in patients with Hirayama disease

OBJECTIVE To investigate changes in soleus H-reflex tests in patients with Hirayama disease (HD) and to analyse correlations between these changes and forward-shifting of the cervical cord during neck flexion. METHODS The amplitude of the soleus H-reflex with and without vibration on the Achilles tendon was recorded bilaterally in 81 HD patients and 34 controls to measure both the vibratory inhibition index (VII) and the Hmax/Mmax ratio. The maximum forward-shifting degree of cervical cord during neck flexion was measured using dynamic magnetic resonance imaging in all HD patients. RESULTS Significantly higher VII was recorded in 6/81 (7.4%) HD patients, along with abnormal Hmax/Mmax ratios in 5 of 6 cases. Compared to illness duration (r = 0.29-0.36, p < 0.05), the maximum forward-shifting degree of the cervical cord was more strongly correlated with both VII and the Hmax/Mmax ratio (r = 0.51-0.81, p < 0.05). CONCLUSIONS HD patients may develop cervical spinal cord injury with disease progression, and these lesions may be more likely to occur in cases with relatively severe cervical-flexion structural abnormalities even during early stages. SIGNIFICANCE More caution should be taken when managing HD patients with severe cervical-flexion abnormalities because of the possible early occurrence of upper motor neuron lesions.

P973: H reflex of flexor carpi radialis is affected in C7, not C6 radiculopathies

We evaluated nerve size and vascularization in median, ulnar, fibular and posterior tibial nerves as well as brachial plexus were bilaterally. We also quantitatively assessed fascicle size and echogenicity. Results: All 18 patients demonstrated nerve enlargement, but no increased vascularization. HNPP demonstrated larger nerves than CMT-1A at sites of entrapment (median nerve at the carpal tunnel p=0.049 and ulnar nerve at the sulcus p<0.001). CMT-1A revealed larger nerves than HNPP, proximal to sites of entrapment (median and fibular nerve, brachial plexus p<0.001). Nerve fascicles where larger (p<0.001) and also more hypo-echogenic in CMT-1A than in HNPP. Nerve and fascicle size, as well as echogenicity did not correlate with age, gender or MRC sum-score. The swelling ratio of HNPP was greater in HNPP than CMT-1 at median (p<0.001), ulnar (p=0.02) and fibular nerve (p<0.001). Conclusions: In CMT-1A enlargement of nerves and fascicles is multifocal among multiple nerves, whereas in HNPP it is restricted to sites of entrapment. The swelling ratio is able to discriminate between HNPP and CMT-1A.