Involvement of sensory fibres in axonal subtypes of Guillain-Barre syndrome.

BACKGROUND: Acute motor axonal neuropathy (AMAN) and acute motor and sensory axonal neuropathy (AMSAN) are due to an antiganglioside antibody mediated attack, thought to be restricted to motor fibres in AMAN. Sensory symptoms and minor sensory conduction abnormalities, however, have been reported in some AMAN patients. OBJECTIVE: To verify whether sensory fibres are truly spared in AMAN and whether AMAN and AMSAN represent a continuum. METHODS: Serial conduction studies in 13 AMAN and three AMSAN patients were reviewed. To evaluate the variation in sensory nerve action potential (SNAP) amplitude in serial recordings, the least significant change in a test-retest study of 20 controls was calculated. Least significant change for median, ulnar and sural nerves were 44%, 47% and 58%, respectively. RESULTS: In 34% of initially normal sensory nerves of six AMAN patients, SNAP amplitude significantly increased by 57-518%. In three nerves of three AMAN patients, SNAP significantly decreased by 50-69%. Overall, serial recordings allowed detection of sensory fibre involvement in 49% of nerves and in 69% of AMAN patients. In one AMSAN patient, SNAP increased in two nerves by 150-300%; in another patient, SNAPs, unrecordable at baseline in six nerves, reappeared during follow-up and normalised in three nerves. In five nerves of three AMAN and in eight nerves of two AMSAN patients, SNAP amplitudes increased rapidly, suggesting reversible conduction failure of sensory fibres. In other nerves, SNAP increased over months, as for axonal regeneration. CONCLUSIONS: Sensory fibres are often involved subclinically in AMAN. Reversible conduction failure may develop in sensory as well as motor fibres in both AMAN and AMSAN. AMAN and AMSAN represent a continuum in axonal GBS.

Pitfalls in electrodiagnosis of Guillain-Barré syndrome subtypes.

OBJECTIVE: To electrophysiologically classify an Italian Guillain-Barré syndrome (GBS) population into demyelinating and axonal subtypes, to investigate how serial recordings changed the classification and to underline the pitfalls in electrodiagnosis of GBS subtypes. METHODS: The authors applied two current electrodiagnostic criteria sets for demyelinating and axonal GBS subtypes in 55 patients who had at least two serial recordings in three motor and sensory nerves. RESULTS: At first test, the electrodiagnosis was almost identical with both criteria: 65-67% of patients were classifiable as acute inflammatory demyelinating polyradiculoneuropathy (AIDP), 18% were classifiable as axonal GBS, and 14-16% were equivocal. At follow-up, 24% of patients changed classification: AIDP decreased to 58%, axonal GBS increased to 38%, and equivocal patients decreased to 4%. The majority of shifts were from AIDP and equivocal groups to axonal GBS, and the main reason was the recognition by serial recordings of the reversible conduction failure and of the length-dependent compound muscle action potential amplitude reduction patterns as expression of axonal pathology. CONCLUSIONS: Axonal GBS is pathophysiologically characterised not only by axonal degeneration but also by reversible conduction failure at the axolemma of the Ranvier node. The lack of distinction among demyelinating conduction block, reversible conduction failure and length-dependent compound muscle action potential amplitude reduction may fallaciously classify patients with axonal GBS as having AIDP. Serial electrophysiological studies are mandatory for proper diagnosis of GBS subtypes and the identification of pathophysiological mechanisms of muscle weakness. More reliable electrodiagnostic criteria taking into consideration the reversible conduction failure pattern should be devised.

Reversible conduction failure in pharyngeal-cervical-brachial variant of Guillain-Barré syndrome.

In two patients with the pharyngeal-cervical-brachial variant (PCB) of Guillain-Barré syndrome (GBS), low amplitude distal compound muscle action potentials and partial motor conduction blocks normalized without development of excessive temporal dispersion within 4 weeks. Sensory nerve action potentials significantly improved in amplitude or, when absent, rapidly became recordable at follow-up. Besides axonal degeneration, PCB is characterized by reversible conduction failure in both motor and sensory fibers and is in the continuous spectrum of axonal GBS subtypes.

A standardized clinical evaluation of patients affected by facioscapulohumeral muscular dystrophy: The FSHD clinical score.

To define numerically the clinical severity of facioscapulohumeral muscular dystrophy (FSHD), we developed a protocol that quantifies muscle weakness by combining the functional evaluation of six muscle groups affected in this disease. To validate reproducibility of the protocol, 69 patients were recruited. Each patient was evaluated by at least five neurologists, and an FSHD severity score was given by each examiner. The degree of agreement among clinicians' evaluations was measured by kappa-statistics. Nineteen subjects received a score between 0 and 1, 9 had a score between 2 and 4, 20 received a score between 5 and 10, and 8 had a score between 11 and 15. Of the 13 subjects with D4Z4 alleles within the normal range (ranging from 10 to 150 repeats), 12 obtained a score of 0 and only 1 had a score of 1. Kappa-statistics showed a very high concordance for all muscle groups. We developed a simple, reliable, easily used tool to define the clinical expression of FSHD. Longitudinal studies will assess its sensitivity and utility in measuring changes for widespread use.

Management of extreme carpal tunnel syndrome: evidence from a long-term follow-up study.

Extreme carpal tunnel syndrome (CTS) is characterized by severe thenar atrophy, plegia of the abductor pollicis brevis (APB), fixed sensory deficit in the median nerve distribution, and absence of median motor and sensory responses on electrophysiological examination. In this study we report long-term follow-up of 37 patients with extreme CTS. Of the 24 patients with idiopathic extreme CTS, 9 were untreated, and 3 received conservative treatment. At follow-up, none of these patients showed objective or electrophysiological improvement, and all but 1 still reported positive symptoms. Conversely, 12 patients (14 hands) who underwent carpal tunnel release showed: resolution of positive symptoms in all but 1 hand; reappearance of median compound muscle action potentials (4.2 +/- 0.6 mV); reappearance of sensory nerve action potentials in all but 1 (7.9 +/- 0.8 microV); improvement of APB strength to grade 4 or 5 on the Medical Research Council scale in 11 hands; and resolution of hypesthesia in 1 hand. Six of 13 patients with non-idiopathic extreme CTS were operated. Of the 6, we found no or poor reinnervation in 3 patients, restoration of nerve responses and normal APB strength but no relief from pain and/or paresthesia in 2, and full recovery in 1. If untreated, extreme CTS is an irreversible condition. Although the outcome is considered to be disappointing in such cases, carpal tunnel release provides long-term relief, significant sensorimotor reinnervation, and improvement of motor deficit in most patients. It should be considered to be the first-choice treatment for idiopathic extreme CTS. Associated diseases do not necessarily imply a poor surgical outcome.