Focal myelin swellings and tomacula in anti-MAG IgM paraproteinaemic neuropathy: Novel teased nerve fiber studies

Focal myelin swellings and tomacula in teased nerve fibers from a case of IgM anti-myelin-associated glycoprotein (MAG) paraproteinaemic neuropathy were examined using a novel technique. Five different morphologic abnormalities were identified--myelin sheath outfolding, myelin sheath infolding, enlargement of the adaxonal space, myelin degeneration, multiple increased concentric loops--and a combination of these structural abnormalities often occur in association with myelin degeneration. Similar structural changes were found in externally normal segments of teased fibers without evidence of myelin swelling or tomacula from the same case. These structural abnormalities are consistent with a disturbance of the normal adhesion functions of MAG in the maintenance of axon-myelin relationships.     

An uncommon cause of bifacial weakness and non-length-dependent demyelinating neuropathy

Tangier disease is a rare metabolic disorder that causes neuropathy in half of the affected individuals. We present the clinical, electrophysiological, and histopathological findings in a middle-aged gentleman of Tangier disease who was initially diagnosed as leprosy and treated with antileprosy drugs. The presence of a demyelinating electrophysiology in a patient with predominant upper limb involvement and facial diplegia should raise the suspicion of Tangier disease. Estimation of serum lipids should form a part of routine evaluation in order to avoid misdiagnosis.     

Novel fibroblastic onion bulbs in a demyelinating avian peripheral neuropathy produced by riboflavin deficiency

Aquaporin-4 (AQP4) has recently been implicated in the pathogenesis of neuromyelitis optica (NMO) where it has been identified as the first defined autoantigen pertinent to an inflammatory demyelinating disorder of the human CNS. Furthermore, a recent case report has shown a lack of AQP4 expression in the spinal cord lesions of NMO. However, the pattern of AQP4 expression in multiple sclerosis (MS) tissues has not been well-defined. In the present investigation we have confirmed a lack of expression of AQP4 in optic and spinal cord lesions in NMO which contrasted sharply with the increased levels of AQP4 expression seen in MS lesions. Furthermore a detailed immunohistochemical and semi-quantitative analysis is used to describe the expression pattern of AQP4 on well-characterized tissue microarray samples of MS and control white matter. Anatomically AQP4 was more highly expressed in all categories of MS tissue compared to normal control tissues with the most abundant expression in active lesions. Within active lesions AQP4 expression was significantly correlated with expression of the pro-inflammatory cytokine osteopontin. At the cellular level dual-labeling immunofluoresence demonstrated that increased expression of AQP4 was most pronounced at the astrocytic endfeet but was also associated with the cell bodies of astrocytes in the tissue parenchyma. The finding of increased AQP4 expression in MS lesions in contrast to the lack of expression in NMO lesions may suggest different mechanisms of initiation and progression between the two disease states.     

Focal myelin thickenings in a peripheral neuropathy associated with IgM monoclonal gammopathy

Summary Nerve biopsy in peripheral neuropathies associated with an IgM monoclonal gammopathy may occasionally display focal myelin thickenings. In a patient with such an IgM neuropathy, in whom an anti-myelin-associated glycoprotein (MAG) antibody activity was present in the serum, single-fiber preparations revealed 34% of internodes bearing myelin swellings. The morphometric, morphological and ultrastructural findings were reminiscent but not identical to those of the hereditary tomaculous neuropathy with liability to pressure palsies. Atypical features for tomacula included lack of spiralization of the redundant loops of myelin around the axons and their predominant external situation with regard to the myelin sheath. The frequent colocalization of myelin thickenings and the widening of myelin lamellae typical of IgM neuropathies, are highly suggestive of some pathogenetic link between the two abnormalities. The redundant loops of myelin in IgM neuropathies possibly result from a defect in the axon-myelin adhesion secondary to the binding of IgM on an epitope of MAG directly involved in cell-cell adhesion.     

Focally folded myelin in Charcot-Marie-Tooth neuropathy type 1B with Ser49Leu in the myelin protein zero

Charcot-Marie-Tooth disease type 1B (CMT1B) is a demyelinating neuropathy caused by mutations in the myelin protein zero (P₀) gene (MPZ). A few cases of CMT1B were recently found to be characterized by focally folded myelin sheaths in nerve biopsy specimens; the significance of this association is unknown. Here, we describe two unrelated pedigrees harboring a heterozygous Ser49Leu substitution in P₀ex. In both pedigrees, the mutation caused a late-onset, relatively mild CMT1B; in one pedigree, two patients had atrophy of peroneal muscles but hypertrophy of the gastrocnemius muscles. The sural nerve biopsy performed in the two index cases revealed an identical chronic demyelinating and remyelinating neuropathy dominated by focal foldings of the myelin sheath shaped either as tomacula or as out/infoldings. The report adds Ser49Leu to the mutations of P₀ex associated with focally folded myelin and provides strong evidence that such a structural alteration of the myelin sheath reflects a distinct pathogenetic mechanism in a subgroup of CMT1B. Received: 18 August 1999 / Revised, accepted: 22 November 1999     

The single-fiber EMG in chronic demyelinating neuropathy

Various parameters of single- fiber electromyography (SFEMG) were studied in 19 patients with electrophysiologically and histologically proven chronic demyelinating neuropathy. The mean duration of disease at the time of testing was four years. Motor nerve conduction in the median nerve was abnormal in all patients, whereas sensory nerve conduction was abnormal in all but one. Needle EMG in the extensor digitorum communis (EDC) muscle showed rare fibrillations and fasciculations and some abnormal motor unit potentials in most of patients. SFEMG in the EDC muscle showed an increased fiber density in seven cases (37%) and minimally abnormal jitter in 14 cases (74%). Single-fiber action potentials were stable, whereas blocking was rare. Fiber density was significantly increased in patients with fibrillation in the conventional needle EMG. Our study showed that the SFEMG is mildly abnormal in many patients with demyelinating neuropathy and that this test is useful in detecting and quantitating axonal degeneration in demyelinating neuropathy.     

Guanethidine adrenergic neuropathy: an animal model of selective autonomic neuropathy

Chronic administration of guanethidine to adult rats induces a selective autoimmune adrenergic neuropathy. Physiological and biochemical features of this disorder in the peripheral nervous system were explored in young adult Sprague-Dawley rats given daily intraperitoneal guanethidine monosulfate for 5 weeks. Control rats received daily saline injections. The guanethidine-treated animals gained less weight, had ptosis, and had a lower mean arterial blood pressure in the supine and upright tilted positions. Norepinephrine was depleted in the peroneal, sural, tibial, and vagal nerves, the nutrient artery to the tibial nerve and in the superior cervical sympathetic ganglion of the drug-treated animals. On light microscopy, there was an inflammatory cell infiltrate and neuron loss in the superior cervical ganglion. Caudal and sciatic-tibial nerve conduction values were well preserved in the guanethidine-treated animals as was the ‘C’ potential derived from unmyelinated vagal fibers recorded in an in vitro chamber. The ‘C’ potential recorded from the cervical sympathetic trunk, however, was reduced in amplitude correlating with the loss of norepinephrine content in the harvested contralateral superior cervical sympathetic ganglion. The findings further support the view that guanethidine produces a selective adrenergic neuropathy in the rat — providing a useful standard with which to gauge autonomic involvement in other models of neuropathy. In addition, loss of the cervical sympathetic ‘C’ potential suggests that this presumed preganglionic structure also contains postganglionic adrenergic fibers.     

Axonal and demyelinating neuropathy with reversible proximal conduction block,an unusual feature of vitamin B12 deficiency

We report a 35-year-old patient with megaloblastic anemia who presented with features of subacute combined degeneration of the cord. Electrophysiological studies showed features of axonal neuropathy. In addition, there was evidence of prominent focal proximal conduction block in several nerves. After treatment with cyanocobalamin the neuropathy improved, and the peripheral nerve conduction block detected earlier disappeared. Reversible nerve conduction block as a feature of vitamin B12 deficiency in man, to our knowledge, has not been reported in literature, so far. © 1998 John-Wiley & Sons, Inc. Muscle Nerve 21:1341–1343, 1998.     

Evidence for macrophage-mediated myelin disruption in an animal model for Charcot-Marie-Tooth neuropathy type 1A

Charcot-Marie-Tooth neuropathy type 1A (CMT 1 A) is the most common inherited neuropathy in humans and is mostly caused by a 1.5-Mb tandem duplication of chromosome 17 comprising the gene for the peripheral myelin protein 22-kDa (PMP 22). Although there are numerous studies on the functional role of PMP 22, the mechanisms of myelin degeneration under PMP 22-overexpression conditions have not yet been fully understood. We have shown previously that in mouse mutants hetero- or homozygously deficient for two other myelin components, P0 and C x 32, respectively, immune cells contribute to the demyelinating neuropathy. To test this possibility for PMP 22 overexpression, we investigated a putative mouse model for CMT 1 A, i.e., the mouse strain C 6 1 mildly overexpressing human PMP 22 in peripheral nerves. Electron microscopic and electrophysiologic investigations revealed that this mouse strain develops pathologic features similar to those found in CMT 1 A patients. A novel finding, however, was the upregulation of CD8- and F4/80-positive lymphocytes and macrophages, respectively, in peripheral nerves. The observation that macrophages enter endoneurial tubes of the mutants and obviously phagocytose morphologically normal myelin strongly suggests that the myelin degeneration is mediated at least partially by these phagocytic cells. By gene array technology and quantitative RT-PCR of peripheral nerve homogenates from PMP 22 mutants, monocyte chemoattractant protein-1 (MCP-1; cc l2) could be identified as a putative factor to attract or activate macrophages that attack myelin sheaths in this model of CMT 1 A.     

Peripheral nerve conductions in relapsing remitting multiple sclerosis (RRMS) patients

PurposeThe purpose of this study was to investigate with Elektromioneurografija (EMNG) whether there is any affection on peripheral nerves in (RRMS) patients.Material and MethodMotor and sensory nerve conductions were studied in the control group including 33 RRMS patients and 25 healthy individuals. Expanded Disability Status Scale (EDSS) scores, mean annual attack frequency, duration of disease and treatments of RRMS patients were recorded.ResultsThere was a statistically significant (p < 0.05) elongation in motor distal latency of the right peroneal nerve, slowing in the left peroneal nerve conduction velocity, and an elongation in the F-wave response in the RRMS group compared to the control group. It was observed that motor nerve conduction velocities were slower, albeit not statistically significant, and F wave latencies were longer than control group.ConclusionThere are studies in the literature related to the association between MS and peripheral neuropathy. In this study, we found demyelinating type changes, differing significantly from the control group, in motor nerve conductions in RRMS patients. There may be demyelinating type affection in peripheral nervous system with common autoimmune mechanism in MS, a demyelinating disease of the central nervous system.     

Sensory peripheral neuropathy of vitamin B12 deficiency: A primary demyelinating disease?

Summary In five patients with peripheral neuropathy due to vitamin B₁₂ deficiency, electrodiagnostic studies demonstrated severe reduction in sensory nerve conduction velocities compatible with a demyelinating disorder affecting sensory nerve fibres. It is suggested that in some patients lack of vitamin B₁₂ may cause primary sensory demyelinating neuropathy.     

A novel myelin protein zero (V136G) homozygous mutation causing late onset demyelinating polyneuropathy with brain white matter lesions

Although less common than peripheral myelin protein 22 (PMP22) duplication, there are mutations in myelin protein zero (MPZ) responsible for Charcot-Marie-Tooth disease (CMT) with a number of different clinical profiles. We report here a novel MPZ homozygous mutation, with a peculiar pattern characterized by a late-onset demyelinating profile. In addition, the patient presented brain white matter lesions seemingly ascribable to the mutation.     

Utility of somatosensory evoked potentials in chronic acquired demyelinating neuropathy

Chronic acquired demyelinating polyneuropathy (CADP) is a heterogeneous syndrome that may be classified into a number of subtypes. Somatosensory evoked potentials (SSEPs) assess proximal segments of sensory nerves, inadequately assessed by routine nerve conduction studies (NCSs). The aim of the present study was to determine the utility of SSEPs in diagnosing and classifying different CADP subtypes. Forty-seven patients with CADP were studied and classified in five groups based on conventional NCSs and SSEPs. Some patients in Group 1 were initially misdiagnosed as having either motor neuron disease or multifocal motor neuropathy due to normal sensory NCSs, but they exhibited abnormal tibial and median nerve SSEPs, as evidenced by marked prolongation or absence of peripheral potentials (N9-median nerve, and N20-tibial nerve). These were reclassified as having chronic inflammatory demyelinating neuropathy (CIDP). In CIDP patients (Group 2), SSEPs were abnormal, thereby confirming the presence of demyelination in the proximal peripheral nerves. Patients with distal acquired demyelinating neuropathy (DADS) (Group 3), as defined by conventional NCS, exhibited abnormal SSEPs when anti-MAG antibodies were present. Anti-MAG-negative DADS patients (Group 3) had normal SSEPs. In the pure sensory ataxic group (Group 4), SSEP studies disclosed poorly formed and delayed cortical potentials with absent lumbar (N20) potentials, thereby suggesting the presence of proximal demyelination. SSEPs were normal in the pure motor CIDP and multifocal motor neuropathy patients (MMN) (Group 5), thereby differentiating asymmetric forms of CIDP from MMN. These findings suggest that SSEPs may be an important complementary investigation to conventional NCSs in the diagnosis of CADP.     

Immunotherapy‐responsive allodynia due to distal acquired demyelinating symmetric (DADS) neuropathy

Introduction: Distal acquired demyelinating symmetric (DADS) neuropathy is a distal variant of chronic inflammatory demyelinating polyradiculoneuropathy. It is characterized by chronic distal symmetric sensory or sensorimotor deficits. Sensory ataxia is a common clinical presentation. Nerve conduction studies typically show markedly prolonged distal motor latencies. Methods: We report 2 patients with chronic progressive generalized pain and fatigue, with normal neurological examinations except for allodynia. Results: Nerve conduction studies were typical of DADS neuropathy. Monoclonal protein studies were negative. Cerebrospinal fluid protein levels were elevated. Sural nerve biopsies revealed segmental demyelination and remyelination. One biopsy had marked endoneurial and epineurial lymphocytic infiltration. Immunomodulatory therapy alleviated the pain and fatigue and markedly improved distal motor latencies in both patients. Conclusions: DADS neuropathy can present with pain and a normal neurological examination apart from allodynia. Nerve conduction studies are necessary for diagnosis. These patients respond to immunotherapy better than typical DADS neuropathy patients with sensory ataxia. Muscle Nerve 54 : 973–977, 2016     

Occurrence of active demyelinating lesions in children with hereditary motor and sensory neuropathy (HMSN) type I

Summary In three children with dominant hereditary motor and sensory neuropathy type I, peripheral nerve biopsy showed the classical lesions of segmental demyelination with remyelination and onion bulb formations. In two cases, ultrastructural examination also demonstrated numerous characteristic features of active demyelination. The presence of active demyelinating lesions suggests an autoimmune attack superimposed on the course of a chronic genetic disease.     

Uncompacted myelin lamellae in two cases of peripheral neuropathy

Summary Peripheral nerve biopsies from two patients with chronic sensorimotor neuropathy were studied. The first case was a non-Hodgkin malignant lymphoma and did not show any dysglobulinemia. The second case had a benign monoclonal gammopathy IgG, Lambda type. Direct immunofluorescence showed no deposits in the first case and slight deposits of anti IgG sera on a few myelinated fibers in the second case. There were numerous fibers showing uncompacted myelin lamellae, 7% in the first case and 4% in the second case. Some of these fibers had axons containing more tubules than filaments. The very few cases reported on neuropathies showing that uncompacted myelin lamellae were frequently associated with dysglobulinemic neuropathy. However, this ultrastructural abnormality of the myelin sheath can be observed without any dysglobulinemia.     

Paraneoplastic demyelinating neuropathy,subacute sensory neuropathy,and anti-hu antibodies: Clinicopathological study of an autopsy case

A patient with anti-Hu antibodies, small-cell lung carcinoma, and autopsy-proven subacute sensory neuropathy had early slowing of motor and sensory conduction velocities. In the peripheral nerves, chronic demyelinating and remyelinating lesions with axonal degeneration were associated with an inflammatory reaction consisting of CD8+ T cells and CD68+ macrophages. On immunohistochemical testing, the patient's serum did not react with normal nerve, suggesting that the Hu proteins were not the target of the inflammatory reaction in the nerve. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:850–857, 1998.     

Axon membrane remodeling in the lead-induced demyelinating neuropathy of the rat

At Aplysia H- and D-type cholinergic neuro-neuronal synapses, application of high concentrations of detergents (Triton X-100 and sodium deoxycholate) depressed synaptic transmission and the postsynaptic response to ionophoretic application of acetylcholine (ACh) or carbachol. However, when very low concentrations of detergents (of the order of 10(-9) M for sodium deoxycholate) were used, the nerve-evoked response as well as the ACh and carbachol ionophoretic responses were facilitated (by at least 200%), but only in H-type cells. This facilitation was similar to that previously observed in the same receptor type when acetylcholinesterase (AChE) was inhibited by various organophosphate or carbamate acetylcholinesterase inhibitors (AChEIs)3. Indeed, the effects of AChEI and detergents were not cumulative. We propose that on H-type synapses detergents may perturb a hypothetical molecular interaction between AChE and the acetylcholine receptor (AChR) by which AChE modulates the ability of the AChR to be activated by ACh or carbachol.