Inflammatory Sensory Polyganglionopathies

Neurophysiological approach to disorders of peripheral nerve

Disorders of the peripheral nerve system (PNS) are heterogeneous and may involve motor fibers, sensory fibers, small myelinated and unmyelinated fibers and autonomic nerve fibers, with variable anatomical distribution (single nerves, several different nerves, symmetrical affection of all nerves, plexus, or root lesions). Furthermore pathological processes may result in either demyelination, axonal degeneration or both. In order to reach an exact diagnosis of any neuropathy electrophysiological studies are crucial to obtain information about these variables. Conventional electrophysiological methods including nerve conduction studies and electromyography used in the study of patients suspected of having a neuropathy and the significance of the findings are discussed in detail and more novel and experimental methods are mentioned. Diagnostic considerations are based on a flow chart classifying neuropathies into eight categories based on mode of onset, distribution, and electrophysiological findings, and the electrophysiological characteristics in each type of neuropathy are discussed.

Mononeuropathy multiplex in association with livedoid vasculitis

Livedoid vasculitis is a chronic dermatological disorder associated with petechiae and recurrent, unusually shaped ulcers that heal to form hyperpigmentated areas and atrophie blanche. This condition is more correctly termed a vasculopathy, rather than a vascultis, and is often associated with an underlying hypercoagulable disorder. We report a patient with livedoid vasculitis and mononeuropathy multiplex. We propose that peripheral nervous system involvement arises from multifocal areas of ischemia due to fibrin and thrombin deposition within both the wall and lumen of vasa nervorum.

Epidermal nerve fiber density in sensory ganglionopathies: clinical and neurophysiologic correlations

We assessed the involvement of somatic unmyelinated fibers in sensory ganglionopathies by skin biopsy and quantitative sensory testing (QST). Sixteen patients with ganglionopathy, 16 with axonal neuropathy, and 15 normal controls underwent skin biopsy at the proximal thigh and the distal leg. Intraepidermal nerve fibers (IENF) were immunostained by antiprotein gene product 9.5, and their linear density was quantified under light microscopy. Confocal microscopy studies with double staining of nerve fibers and basement membrane were also performed. Healthy subjects and neuropathy patients showed the typical proximodistal gradient of IENF density; in neuropathies, values were significantly lower at the distal site of the leg, confirming the length-dependent loss of cutaneous innervation. Conversely, ganglionopathy patients with hyperalgesic symptoms did not show any change of IENF density between the proximal thigh and the distal leg. The distinct pattern of epidermal denervation seen in sensory ganglionopathy reflected the degeneration of somatic unmyelinated fibers in a fashion that was not length-dependent, which was consistent with both clinical and neurophysiologic observations and supported the diagnosis.

Wartenberg's migrant sensory neuritis

We describe a patient with the sudden onset of a painful, purely sensory, mononeuritis multiplex. Investigations showed no evidence for any underlying systemic condition. A nerve biopsy showed fascicular wallerian degeneration with perineurial thickening, inflammatory cells, and immunoglobulin G (IgG) deposition. His painful sensory deficits persisted, with no improvement after treatment with prednisone. The clinical characteristics in this case were very similar to those originally described by Wartenberg, and subsequently by other investigators. The investigations in our case strongly suggest that there may be an underlying immune pathogenesis for cases of Wartenberg's migrant sensory neuritis.

Acquired peripheral neuropathy

This article reviews the acquired causes of polyneuropathy other than diabetic and acute-onset neuropathies. The author gives a general method to simplify the diagnosis of chronic polyneuropathy. The acquired polyneuropathies are discussed under four main headings: metabolic disorders, toxic or deficiency states, infections, and immune-mediated. Recent advances in therapy are emphasized, and some illustrative case histories are provided.

Management of painful paraneoplastic syndromes

The majority of patients with advanced malignant disease experience pain, so pain is commonly present in patients with paraneoplastic syndromes. It is rare, however, that the pain itself is a paraneoplastic manifestation of cancer. Usually, the pain in this context is associated with a paraneoplastic syndrome but is not a direct result of that syndrome. Three syndromes in which pain is part of the syndrome and a paraneoplastic manifestation of malignant disease--neuropathy, ganglionitis, and monolitis--have been described in the literature. These syndromes and their management are discussed in this article.

The Trk family of neurotrophin receptors

Accumulating evidence indicates that the Trk family of tyrosine protein kinase receptors, Trk (also known as TrkA), TrkB, and TrkC, are responsible for mediating the trophic effects of the NGF family of neurotrophins. Nerve growth factor (NGF) specifically recognizes Trk, a receptor identified in all major NGF targets, including sympathetic, trigeminal, and dorsal root ganglia as well as in cholinergic neurons of the basal forebrain and the striatum. Brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4) specifically activate the TrkB tyrosine kinase receptor. trkB transcripts encoding this receptor are found throughout multiple structures of the central and peripheral nervous system. Neurotrophin-3 (NT-3) primarily activates the TrkC tyrosine protein kinases, four related isoforms encoded by alternative splicing of trkC, a gene also widely expressed throughout the mammalian nervous system. Unlike the other neurotrophins, NT-3 appears to be somewhat promiscuous since it can activate Trk and TrkB kinase receptors, at least in certain cell systems. The trkB and trkC genes also encode noncatalytic neurotrophin receptor isoforms of an as yet, unknown function. Recently, strains of mice lacking each of these tyrosine kinase receptors have been generated. Preliminary characterization of these mutant mice has provided significant information regarding the role of these receptors in the ontogeny of the mammalian nervous system. For instance, mice deficient for Trk receptors lack most sympathetic neurons and do not display nociceptive and temperature sensations, two defects likely to result from severe neuronal cell loss in their trigeminal and dorsal root ganglia. Mice lacking TrkB tyrosine kinase receptors die postnatally due to their inability to intake food. Neuron cell loss in their trigeminal, nodose and petrosal sensory ganglia as well as in the facial motor nucleus are likely to contribute to this phenotype. Finally, TrkC-deficient mice display strikingly abnormal movements consistent with loss of proprioception, a defect likely to be a consequence of the complete loss of Ia muscle afferents observed in this mutant mice.

Treatable gait disorder and polyneuropathy associated with high titer serum IgM binding to antigens that copurify with myelin-associated glycoprotein

We studied clinical and electrodiagnostic features of 9 patients with very high titers (> 1:10,000) of serum IgM binding to a CNS myelin antigen (CMA) preparation that copurified with myelin-associated glycoprotein (MAG). We found that 8 of the 9 patients had a combined syndrome of gait ataxia and polyneuropathy (GAPN) with late-age onset (mean = 70 years of age). In the 8 GAPN patients progressive difficulty with ambulation led to significant functional disability and frequent falling. Examination showed a wide-based unsteady gait, especially when standing still or turning. There was mild-to-moderate distal sensory loss with involvement of joint position sense only in the toes. Motor changes, when present, were mild and mainly involved distal leg musculature. Treatment of 5 GAPN patients resulted in clear improvement of 2 after intravenous human immunoglobulin and of 3 others after other immunodulating agents. Immune-mediated GAPN syndromes with high titers of serum IgM binding to CMA appear to be treatable causes of gait disorders in older patients.

Lack of neurotrophin-3 leads to deficiencies in the peripheral nervous system and loss of limb proprioceptive afferents

Neurotrophin-3-deficient (NT-3-deficient) mice were generated by gene targeting. Mutant mice displayed severe movement defects of the limbs, and most died shortly after birth. Substantial portions of peripheral sensory and sympathetic neurons were lost while motor neurons were not affected. Significantly, spinal proprioceptive afferents and their peripheral sense organs (muscle spindles and Golgi tendon organs) were completely absent in homozygous mutant mice. This correlated with a loss of parvalbumin and carbonic anhydrase-positive neurons in the dorsal root ganglion. No gross abnormalities were seen in Pacinian corpuscles, cutaneous afferents containing substance P and calcitonin gene-related peptide, and deep nerve fibers in the joint capsule and tendon. Importantly, the number of muscle spindles in heterozygous mutant mice was half of that in control mice, indicating that NT-3 is present at limiting concentrations in the embryo.

Disruption of the neurotrophin-3 receptor gene trkC eliminates la muscle afferents and results in abnormal movements

The trkC gene is expressed throughout the mammalian nervous system and encodes a series of tyrosine protein kinase isoforms that serve as receptors for neurotrophin-3 (NT3), a member of the nerve growth factor (NGF) family of neurotrophic factors. One of these isoforms, gp145trkC/TrkC K1, mediates the trophic properties of NT3 in cultured cells. Here we show that homozygous mice defective for TrkC tyrosine protein kinase receptors lack Ia muscle afferent projections to spinal motor neurons and have fewer large myelinated axons in the dorsal root and posterior columns of the spinal cord. These mice display abnormal movements and postures, indicating that NT3/TrkC-dependent sensor; neurons may play a primary role in proprioception, the sense of position and movement of the limbs.