iMAX: A new tool for assessment of motor axon excitability. A multicenter prospective study.

OBJECTIVE: This study was undertaken to establish by a multicentric approach the reliability of a new technique evaluating motor axon excitability. METHODS: The minimal threshold, the lowest stimulus intensity allowing a maximal response by 1 mA increments (iUP) and then by 0.1 mA adjustments (iMAX) were prospectively derived from three nerves (median, ulnar, fibular) in four university centers (Liège, Marseille, Fraiture, Nice). iMAX procedure was applied in 28 healthy volunteers (twice) and 32 patients with Charcot-Marie-Tooth (CMT1a), chronic inflammatory demyelinating polyneuropathy (CIDP), Guillain-Barré syndrome (SGB) or axonal neuropathy. RESULTS: Healthy volunteers results were not significantly different between centers. Correlation coefficients between test and retest were moderate (> 0.5). Upper limits of normal were established using the 95th percentile. Comparison of volunteers and patient groups indicated significant increases in iMAX parameters especially for the CMT1a and CIDP groups. In CMT1a, iMAX abnormalities were homogeneous at the three stimulation sites, which was not the case for CIDP. CONCLUSIONS: The iMAX procedure is reliable and allows the monitoring of motor axon excitability disorders. SIGNIFICANCE: The iMAX technique should prove useful to monitor motor axonal excitability in routine clinical practice as it is a fast, non-invasive procedure, easily applicable without specific software or devices.

Guillain-Barré Syndrome.

Guillain-Barré syndrome is an acute inflammatory immune-mediated polyradiculoneuropathy presenting typically with tingling, progressive weakness, and pain. Variants and formes frustes may complicate recognition. The best known variant is the sensory ataxic form of Miller Fisher syndrome, which also affects the oculomotor nerves and the brain stem. Divergent pathologic mechanisms lead to demyelinating, axonal, or mixed demyelinating-axonal damage. In the demyelinating form, yet to be identified antigens are inferred by complement activation, myelin destruction, and macrophage-activated cleanup. In the axonal and Miller Fisher variants, gangliosides (GM1, GD1a, GQ1b) are targeted by immunoglobulins and share antigenic epitopes with some bacterial and viral antigens. Campylobacter jejuni infection is associated with an axonal-onset variant; affected patients commonly experience more rapid deterioration. Many other antecedent infectious agents have been recognized including the most recently identified, Zika virus. Supportive care remains the mainstay of therapy. Plasma exchange or intravenous immunoglobin hastens recovery. Combination immunotherapy is not more effective, and the efficacy of prolonged immunotherapy is unproven. One in 3 patients will have deterioration severe enough to require prolonged intensive care monitoring or mechanical ventilation. Full recovery is often seen; most patients regain ambulation, even in severe cases, but disability remains in up to 10% and perhaps more. Numerous challenges remain including early identification and control of infectious triggers, improved access of modern neurointensive care worldwide, and translating our understanding of pathogenesis into meaningful preventive or assistive therapies. This review provides a historical perspective at the centenary of the first description of the syndrome, insights into its pathogenesis, triage, initial immunotherapy, and management in the intensive care unit.

Electrophysiological assessment of Guillain-Barré syndrome with both Gal-C and ganglioside antibodies; tendency for demyelinating type.

Whether patients who have GBS with antibodies to galactocerebroside (Gal-C) and gangliosides (Gal-C-GS-GBS) more often have demyelinating or axonal neuropathy remains controversial. We assessed the electrophysiological data from 16 patients with Gal-C-GS-GBS based on the two established criteria to clarify this issue. In this largest cohort of Gal-C-GS-GBS, eight patients had demyelinating neuropathy and none exhibited axonal neuropathy on either criterion. These data indicated that antibodies to Gal-C, a myelin antigen, might predominantly be associated with demyelinating neuropathy, even in the presence of concomitant antibodies to gangliosides.

Respiratory Muscle Assessment in Acute Guillain-Barré Syndrome.

PURPOSE: Guillain-Barré Syndrome (GBS) is a life-threatening disease due to respiratory muscle involvement. This study aimed at objectively assessing the course of respiratory muscle function in GBS subjects within the first week of admission to an intensive care unit. METHODS: Medical Research Council Sum Score (MRC-SS), vigorimetry, spirometry, and respiratory muscle function tests (inspiratory/expiratory muscle strength: PImax/PEmax, sniff nasal pressure: SnPna) were assessed twice daily. GBS Disability Score (GBS-DS) was assessed once daily. On days one (d1) and seven (d7), blood gases and twitch mouth pressure during magnetic phrenic nerve stimulation (Pmo,tw) were additionally evaluated. RESULTS: Nine subjects were included. MRC-SS, vigorimetry, PImax, and SnPna increased between d1 and d7. GBS-DS, spirometry and Pmo,tw remained unaltered. Only SnPna correlated closely with the MRC-SS on both d1 (r = 0.77, p = 0.02) and d7 (r = 0.74, p = 0.02). CONCLUSION: SnPna was the only parameter that correlated with MRC-SS, while the current gold standard of spirometry measurement did not.

Long term clinical and electrophysiological assessment of Croatian children with corticospinal tract involvement in Guillain-Barré syndrome (GBS).

Guillain-Barré syndrome (GBS) is characterized by areflexia. Hyperreflexia is reported in acute motor axonal neuropathy (AMAN). We present 16 children with GBS at the age of 14 months to 13 years. All children studied fulfilled accepted diagnostic criteria for GBS. Hyperreflexia or positive Babinski sign were obtained in all children studied during follow up. Brain and spinal cord MR scans did not reveal any significant structural and morphological abnormalities of central nervous system. The children were examined clinically and electromyoneurographically 2-5 times successively during 1-8.5 years of follow-up. According to established electrodiagnostic criteria demyelinating form of GBS was most common (68%) compared to axonal (18,7%) or mixed form (12,5%). No children had antecendent Campylobacter jejuni infection. Antiganglioside antibodies were detected in 18,7% of patients associated with demyelinating or mixed (axonal/demyelinating) form. Time to nadir and recovery period of walking ability is prolonged more often in demyelinating GBS. Clinical improvement occur earlier compared to improvement of abnormal electrophysiological parameters.Outcome was excellent in 11 in the period 1 month-8.5 years. Hyperreflexia usually appeared in recovery period suggesting involvement of upper motor neurons or spinal interneurons occurring in Croatian children with both demyelinating and axonal form of GBS usually associated with milder course of disease.

[Isokinetic assessment of muscular strength in subjects with acute inflammatory demyelinating polyradiculoneuropathy]. / Evaluation isocinétique de la force musculaire de patients atteints de polyradiculonévrite aiguë.

OBJECTIVE: To evaluate the feasibility and the interest of isokinetic measures tests in subjects with inflammatory demyelinating polyradiculoneuropathy or Guillain-Barré syndromes (GBS). METHODS: Nine patients with GBS are tested at the beginning and after 6 months of recovery stage. They benefit from (1) isokinetic assessment of muscular strength of knee, elbow, ankle: flexion/extension and shoulder abduction/adduction ranging 30 per s at 180 per s angular velocity; (2) isometric assessment of the same muscular groups; (3) manual muscle testing; (4) functional independence measure. RESULTS: Isokinetic tests were tolerated at 60 and 120 per s. Fatigability appears since the third second of isometric test. The relationships between isokinetic, manual tests and isometric tests are variables (0.29 < r < 0.97). The evaluation after 6 months of recovery showed a good sensibility of isokinetic test. CONCLUSION: The continuation of this motor isokinetic evaluation, in a large population, will permit to establish longitudinal and evolutive profile of each patient and will facilitate to chose the rehabilitation program.

Assessment of coronary morphology and flow in a patient with Guillain-Barré syndrome and ST-segment elevation.

Patients with Guillain-Barré syndrome often have cardiac disturbances as a manifestation of autonomic dysfunction. Such abnormalities consist of arrhythmias and disturbances of heart rate and blood pressure. We report a case of a patient with Guillain-Barré syndrome who developed ST-segment elevation in the inferolateral leads, suggestive of an acute coronary syndrome. Cardiac catheterization revealed angiographically normal coronary arteries. Intracoronary ultrasound was also normal. Intracoronary Doppler flow measurements revealed an elevated baseline coronary flow velocity of up to 41 cm/s and decreased coronary flow reserve, particularly in the left circumflex artery. Myopericarditis as cause of the electrocardiographic changes could be ruled out by echocardiography and endomyocardial biopsy. We postulate that the intracoronary Doppler findings are caused by autonomic dysfunction with decrease of coronary resistance and redistribution of the transmural myocardial blood flow.