Small fiber neuropathy: a common and important clinical disorder

Small fiber neuropathy (SFN) is a neuropathy selectively involving small diameter myelinated and unmyelinated nerve fibers. Interest in this disorder has considerably increased during the past few years. It is often idiopathic and typically presents with peripheral pain and/or symptoms of autonomic dysfunction. Diagnosis is made on the basis of the clinical features, normal nerve conduction studies (NCS) and abnormal specialized tests of small nerve fibers. Among others, these tests include assessment of epidermal nerve fiber density, temperature sensation tests for sensory fibers and sudomotor and cardiovagal testing (QSART) for autonomic fibers. Unless an underlying disease is identified, treatment is usually symptomatic and directed towards alleviation of neuropathic pain.     

Dysfunction at the motor end-plate and axon membrane in Guillain-Barré syndrome: a single-fiber EMG study

In nine patients with Guillain-Barré syndrome (GBS), stimulation single-fiber electromyography (SFEMG) and serological studies were performed in the acute stage of the illness. Increased jitter and intermittent blocking of muscle fiber action potentials occurred to a varying degree in all patients. Five patients had elevated titers of antiganglioside antibodies. The most remarkable EMG phenomenon was the occurrence in all patients of impulse blocking at normal or slightly increased jitter. The assumption that this phenomenon was due to an axolemmal dysfunction was confirmed by the occurrence in two patients of concomitant blocking of two muscle fiber action potentials at strictly normal jitter values. In one patient this sign of axonal dysfunction was demonstrated with SFEMG at voluntary activation. In another patient, concomitant blocking was associated with greatly increased but completely independent jitter of both components. The results of this study show that both a disorder of neuromuscular transmission and an axolemmal dysfunction play a role in the pathophysiology of GBS.     

Postsurgical pain and weakness in the shoulder-arm region: iatrogenic or not?

Four patients, one man aged 66 years and three women aged 69, 33 and 55 years, respectively, had postsurgical pain and weakness in the shoulder-arm region. Initially, a peripheral nerve lesion on a mechanical basis was suspected in all patients. However, because of the sharp pain starting after a postsurgical pain-free interval ranging from a few hours to two days, followed after some time by local muscular weakness, the diagnosis 'neuralgic amyotrophy' was made later. The electromyographic findings were in agreement with this diagnosis. The chronological sequence of the symptoms only became clear after targeted questioning. After 6-24 months, the strength was more or less restored. Usually, the prognosis of neuralgic amyotrophy is favourable, although full functional recovery may take two to three years and in a minority of cases recovery remains incomplete. Early diagnosis is important because of the prognostic aspects and to prevent unnecessary investigations or even surgical explorations, as well as legal claims. Therefore, not only neurologists but particularly surgeons and anaesthesiologists should be aware of this postsurgical condition.     

Radial tunnel syndrome. An investigation of compression neuropathy as a possible cause.

Conventional electromyographic and nerve-conduction studies usually do not show abnormalities in patients who have a clinical diagnosis of radial tunnel syndrome. Therefore, posterior interosseous nerve-conduction measurements were performed during forced supination in patients who had this syndrome. Only one of sixteen patients had a major increase in latency. Our data do not support the hypothesis that the signs and symptoms in most patients who have a diagnosis of radial tunnel syndrome are caused by compression of the posterior interosseous nerve.     

Overexpression of rapsyn in rat muscle increases acetylcholine receptor levels in chronic experimental autoimmune myasthenia gravis

The primary autoantigen in myasthenia gravis, the acetylcholine receptor (AChR), is clustered and anchored in the postsynaptic membrane of the neuromuscular junction by rapsyn. Previously, we found that overexpression of rapsyn by cDNA transfection protects AChRs in rat muscles from antibody-mediated loss in passive transfer experimental autoimmune myasthenia gravis (EAMG). Here, we determined whether rapsyn overexpression can reduce or even reverse AChR loss in muscles that are already damaged by chronic EAMG, which mimics the human disease. Active immunization against purified AChR was performed in female Lewis rats. Rapsyn overexpression resulted in an increase in total muscle membrane AChR levels, with some AChR at neuromuscular junctions but much of it in extrasynaptic membrane regions. At the ultrastructural level, most endplates in rapsyn-treated chronic EAMG muscles showed increased damage to the postsynaptic membrane. Although rapsyn overexpression stabilized AChRs in intact or mildly damaged endplates, the rapsyn-induced increase of membrane AChR enhanced autoantibody binding and membrane damage in severe ongoing disease. Thus, these results show the complexity of synaptic stabilization of AChR during the autoantibody attack. They also indicate that the expression of receptor-associated proteins may determine the severity of autoimmune diseases caused by anti-receptor antibodies.     

Partial trapeziectomy and interposition of fascia lata allograft in the operative treatment of thumb base osteoarthritis

Aim: The purpose of this retrospective cohort study was to evaluate the results of fascia lata allograft interposition after partial trapeziectomy in patients with symptomatic first carpometacarpal joint osteoarthritis. Methods and results: Twenty-one patients (22 thumbs) with Eaton-Glickel stage II or III first carpometacarpal joint osteoarthritis were included. After a mean follow-up duration of 70.2 months, most patients experienced minimal pain. The operation was graded excellent or good by 15 patients (15 hands). Active range of motion and strength measurements were comparable to the contralateral hand, except for extension, which was slightly better in the contralateral hand. The mean radiologically measured difference pre- and postoperatively in distance between distal part of the trapezium and base of the metacarpal was 2.7 mm. Two patients had reoperations in the first year after the initial operation because of ongoing pain. Conclusion: Partial trapeziectomy with interposition of fascia lata allograft in patients with symptomatic first carpometacarpal joint osteoarthritis can achieve reasonable results. It may be considered a reliable operative treatment option in patients with first carpometacarpal joint osteoarthritis.