Differences in nerve excitability properties between isolated bulbar palsy and bulbar-dominant amyotrophic lateral sclerosis.

Objectives: Isolated bulbar palsy (IBP) is a rare variant that can show a benign course, while progressive bulbar palsy (PBP) has been regarded as a bulbar-dominant type of classical amyotrophic lateral sclerosis (cALS). This study aimed to identify differences in the excitability properties between them.Methods: We consecutively collected data on 22 ALS patients: 13 with cALS, 5 with PBP, and 4 with IBP. An automated nerve excitability test (NET) was applied to measure the strength-duration time constant, threshold electrotonus (TE), current-threshold relationship, and recovery cycle. The axonal excitability properties were compared between the ALS groups and 25 controls.Results: Compared to controls, the cALS group showed a greater change in the depolarizing phase of TE of 90-100 ms after depolarizing current [TEd(90-100)] (53.3±1.3 [mean±SEM] for cALS and 49.0±0.7 for control, P<0.01) and lower S2 accommodation (19.6±0.8 and 22.6±0.7, respectively; P=0.01). There was a nonsignificant tendency for a high TEd(90-100) pattern to be less prominent in the IBP group than in the PBP group (51.5±4.22 and 48.8±1.5, respectively). In addition, all of the parameters of nerve excitability other than S2 accommodation in the PBP and IBP groups did not differ significantly from those in the controls.Conclusions: The excitability properties of IBP and PBP differ from those of cALS. The pattern of NET in PBP was more similar to that in cALS than that in IBP. These findings suggest that IBP is a different entity from bulbar-dominant ALS and PBP.

Early discrimination of sensorimotor Guillain-Barré syndrome into demyelinating or axonal subtype by automated nerve excitability testing.

In the early stage of disease, differentiating acute inflammatory demyelinating polyneuropathy (AIDP) and acute motor sensory axonal neuropathy (AMSAN) using only a conventional nerve conduction studies (NCS) may be difficult. We evaluated the differences in the motor axonal excitability properties of 16 cases of sensorimotor Guillain-Barré syndrome by nerve excitability testing (NET). The antiganglioside antibody assay and follow-up NCS resulted in 12 patients diagnosed as AIDP and 4 patients as AMSAN. Clinical and excitability parameters in each group were compared with those in 30 normal controls. Automated NET with threshold tracking techniques was used to calculate the strength-duration time constant (SDTC), threshold electrotonus (TE), current-threshold relationship (CTR), and recovery cycle (RC) of excitability. Except for subtle changes in excitability parameters, AIDP showed no definitive difference relative to normal controls. Comparison between AMSAN and normal controls also revealed no significant differences in the SDTC, TE, and CTR parameters. However, there were clear differences in some of the RC parameters: the relative refractory period was significantly longer in the AMSAN group than in the AIDP group (4.40 ± 1.11 vs. 3.09 ± 1.01 ms, mean ± SEM; p < 0.001), while superexcitability was significantly less prominent in the AMSAN group (-6.80 ± 10.30 vs. -26.48 ± 1.17%, mean ± SEM; p < 0.001). Our study identified that both AIDP and AMSAN were associated with subtle changes in excitability properties. Nonetheless, the prominent increase in refractoriness in AMSAN suggests the presence of a nodal conduction block.

Relative sparing of the second lumbrical muscle in carpal tunnel syndrome is not associated with regional differences in axonal membrane potential.

OBJECTIVE: Regional differences in nerve resting membrane potential have been associated with susceptibility to entrapment neuropathy. The aim of this study was to test whether the different susceptibilities to carpal tunnel syndrome (CTS) of median nerve motor axons supplying the second lumbrical (L2) and abductor pollicis brevis (APB) muscles could be explained in this way. METHODS: Computerized nerve-excitability testing was used to examine the excitability properties of the median motor axons of both L2 and APB in 24 healthy volunteers. RESULTS: Although some excitability measurements differed between the L2 and APB motor axons, estimates of resting membrane potential (RMP) by model fitting indicated no significant difference between the two groups. CONCLUSION: Differences in RMP cannot account for the relative sparing of L2 axons in severe CTS. SIGNIFICANCE: L2 sparing in CTS most likely has an anatomical rather than a biophysical basis.

Recurrent Guillain-Barré syndrome presenting stereotypic manifestations, positive antiganglioside antibodies, and rapid recovery.

OBJECTIVE: Recurrent Guillain-Barré syndrome (rGBS) has been described as a rare entity with distinct characteristics. However, little is known about rGBS in Asian group. The aim of this study was to identify the incidence and clinical course of rGBS, and to determine its clinical/pathophysiological implications. METHODS: The consecutive data of 117 GBS patients were retrieved from a single university-based hospital in Korea and analyzed in terms of clinical, serological, electrophysiological aspects. RESULTS: A thorough review revealed that three (2.6%) of the enrolled patients had experienced more than two definite recurrent attacks of GBS. Interestingly, all three cases exhibited clinically stereotypical features, serum antiganglioside antibodies, and rapid recovery after intravenous immunoglobulin treatment. Clinical, serological, and electrophysiological features of rGBS cases were described in detail. CONCLUSION: The stereotypic presentation of each attack in this variant suggests the importance of both host and genetic factors for the clinical manifestations. In addition, the simultaneous presence of serum antiganglioside antibodies and rapid recovery implicate reversible nerve conduction failure as the mechanism of rGBS. These features are different from typical monophasic GBS and acute onset of chronic inflammatory demyelinating polyneuropathy.

First-ever optic neuritis: distinguishing subsequent neuromyelitis optica from multiple sclerosis.

To identify factors distinguishing subsequent neuromyelitis optica (NMO) from multiple sclerosis (MS) after first-ever optic neuritis (ON), we compared ophthalmic findings and MRI features of 24 NMO and 55 MS patients who initially presented with ON. The female-to-male ratio was higher, and bilateral ON was more common in NMO patients than in MS patients (p = 0.044 and p = 0.020, respectively). The visual acuity (VA) score was higher in NMO patients (p = 0.034), and a greater proportion of NMO patients had a VA score ≥ 5 (p = 0.003). The frequency of patients without pattern-reversal and flash visual evoked potentials was higher in the NMO group (p = 0.015). Brain MRI abnormalities were more common in the MS group (p = 0.001). The optic chiasm was affected in 25 % of NMO patients and was unaffected in MS patients, although it did not reach statistical significance (p = 0.096). There were no differences with respect to the severity of swelling and enhancement of the optic nerve. In conclusion, severe optic nerve damage at the first ON attack was associated with subsequent development of NMO, whereas presence of brain MRI abnormalities was associated with developing MS.

Factors associated with the effectiveness of plasma exchange for the treatment of NMO-IgG-positive neuromyelitis optica spectrum disorders.

To identify factors associated with plasma exchange response in neuromyelitis optica (NMO) spectrum disorders, the clinical and magnetic resonance imaging (MRI) features of 31 NMO-IgG-positive patients receiving plasma exchange for steroid-resistant exacerbations were analyzed. Functional improvement was observed in 65% of the patients. A lower baseline Expanded Disability Status Scale score was associated with favorable response (p = 0.040). Patients without cord atrophy had a higher success rate than patients with atrophy (p = 0.016). Levels of NMO-IgG did not differ between responders and non-responders before and after plasma exchange. In conclusion, a minimal pre-existing disability is the primary determinant of the effectiveness of plasma exchange.