Hans-Michael Meinck

A TRANSGENIC RAT MODEL OF CHARCOT-MARIE-TOOTH DISEASE

Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy in humans and has been associated with a partial duplication of chromosome 17 (CMT type 1A). We have generated a transgenic rat model of this disease and provide experimental evidence that CMT1A is caused by increased expression of the gene for peripheral myelin protein-22 (PMP22, gas-3). PMP22-transgenic rats develop gait abnormalities caused by a peripheral hypomyelination, Schwann cell hypertrophy (onion bulb formation), and muscle weakness. Reduced nerve conduction velocities closely resemble recordings in human patients with CMT1A. When bred to homozygosity, transgenic animals completely fail to elaborate myelin. We anticipate that the CMT rat model will facilitate the identification of a cellular disease mechanism and serve in the evaluation of potential treatment strategies.

Stiff man syndrome and related conditions

The stiff man syndrome (SMS) and its variants, focal SMS, stiff limb (or leg) syndrome (SLS), jerking SMS, and progressive encephalomyelitis with rigidity and myoclonus (PERM), appear to occur more frequently than hitherto thought. A characteristic ensemble of symptoms and signs allows a tentative clinical diagnosis. Supportive ancillary findings include (1) the demonstration of continuous muscle activity in trunk and proximal limb muscles despite attempted relaxation, (2) enhanced exteroceptive reflexes, and (3) antibodies to glutamic acid decarboxylase (GAD) in both serum and spinal fluid. Antibodies to GAD are not diagnostic or specific for SMS and the role of these autoantibodies in the pathogenesis of SMS/SLS/PERM is the subject of debate and difficult to reconcile on the basis of our present knowledge. Nevertheless, evidence is emerging to suggest that SMS/SLS/PERM are manifestations of an immune‐mediated chronic encephalomyelitis and immunomodulation is an effective therapeutic approach.

Stiff person syndrome-associated autoantibodies to amphiphysin mediate reduced GABAergic inhibition

Synaptic inhibition is a central factor in the fine tuning of neuronal activity in the central nervous system. Symptoms consistent with reduced inhibition such as stiffness, spasms and anxiety occur in paraneoplastic stiff person syndrome with autoantibodies against the intracellular synaptic protein amphiphysin. Here we show that intrathecal application of purified anti-amphiphysin immunoglobulin G antibodies induces stiff person syndrome-like symptoms in rats, including stiffness and muscle spasms. Using in vivo recordings of Hoffmann reflexes and dorsal root potentials, we identified reduced presynaptic GABAergic inhibition as an underlying mechanism. Anti-amphiphysin immunoglobulin G was internalized into neurons by an epitope-specific mechanism and colocalized in vivo with presynaptic vesicular proteins, as shown by stimulation emission depletion microscopy. Neurons from amphiphysin deficient mice that did not internalize the immunoglobulin provided additional evidence of the specificity in antibody uptake. GABAergic synapses appeared more vulnerable than glutamatergic synapses to defective endocytosis induced by anti-amphiphysin immunoglobulin G, as shown by increased clustering of the endocytic protein AP180 and by defective loading of FM 1-43, a styryl dye used to label cell membranes. Incubation of cultured neurons with anti-amphiphysin immunoglobulin G reduced basal and stimulated release of γ-aminobutyric acid substantially more than that of glutamate. By whole-cell patch-clamp analysis of GABAergic inhibitory transmission in hippocampus granule cells we showed a faster, activity-dependent decrease of the amplitude of evoked inhibitory postsynaptic currents in brain slices treated with antibodies against amphiphysin. We suggest that these findings may explain the pathophysiology of the core signs of stiff person syndrome at the molecular level and show that autoantibodies can alter the function of inhibitory synapses in vivo upon binding to an intraneuronal key protein by disturbing vesicular endocytosis.

Severe forward flexion of the trunk in Parkinson's disease: Focal myopathy of the paraspinal muscles mimicking camptocormia

Pronounced forward flexion of the trunk, often termed camptocormia, is a typical symptom of patients with Parkinsons disease. In 4 parkinsonian patients with camptocormia, paraspinal muscles were studied by electromyography (EMG) and axial computerized tomography (CT) or magnetic resonance imaging (MRI) scans and muscle biopsy. EMG of the lumbar and thoracic paravertebral muscles showed abundant fibrillations, positive sharp waves, and bizarre high‐frequency discharges. Spinal CT and MRI scans revealed variable degrees of atrophy and fatty replacement of the thoracolumbar paraspinal muscles on both sides. No other signs of neuromuscular disease were found. Biopsy of the paraspinal muscles revealed end‐stage myopathy with autophagic vacuoles, chronic inflammatory myopathy, unspecific myopathic changes, or mitochondrial myopathy. In parkinsonian patients with pronounced forward flexion of the trunk, myopathy confined to the erector spinae muscles must be considered.

Stiff man syndrome: Clinical and laboratory findings in eight patients

The clinical, biochemical, neuroimaging and neurophysiological findings of eight patients with stiff man syndroms (SMS) [four of six being tested with autoantibodies against glutamic acid decarboxylase (GAD)] are presented. In two patients (one GAD-positive, one GAD-negative), transient oculomotor disturbances suggested progressive encephalomyelitis with rigidity and myoclonus (PERM) as differential diagnosis. The catalogue of characteristic clinical symptoms of SMS is extended by three new symptoms: (1) an aura-like feeling reported by five patients to precede spontaneous spasmodic attacks; (2) a stereotyped motor pattern seen in seven patients during spasmodic jerks, consisting of brief opisthotonos, stiffening of the slightly abducted legs and inversion of the plantar-flexed feet; (3) a paroxysmal fear when crossing a free space unaided, or even thinking of it. Clinical findings did not enable us to discriminate between patients tested GAD-positive or GAD-negative. Cerebrospinal fluid contained elevated immunoglobulin levels or cell counts, or both, in the majority of patients. Autopsy of one patient revealed scattered lymphocyte cuffs around leptomeningeal, intracerebral and particularly intraspinal vessels, suggesting a mild inflammatory process. Whether SMS and PERM are closely related is discussed; they are possibly both manifestations of a spectrum of encephalomyelopathies having autoimmunity against GABAergic neurons in common.

Anterior interosseous nerve syndrome Fascicular motor lesions of median nerve trunk

Objective: We sought to determine lesion sites and spatial lesion patterns in spontaneous anterior interosseous nerve syndrome (AINS) with high-resolution magnetic resonance neurography (MRN). Methods: In 20 patients with AINS and 20 age- and sex-matched controls, MRN of median nerve fascicles was performed at 3T with large longitudinal anatomical coverage (upper arm/elbow/forearm): 135 contiguous axial slices (T2-weighted: echo time/repetition time 52/7,020 ms, time of acquisition: 15 minutes 48 seconds, in-plane resolution: 0.25 × 0.25 mm). Lesion classification was performed by visual inspection and by quantitative analysis of normalized T2 signal after segmentation of median nerve voxels. Results: In all patients and no controls, T2 lesions of individual fascicles were observed within upper arm median nerve trunk and strictly followed a somatotopic/internal topography: affected were those motor fascicles that will form the anterior interosseous nerve further distally while other fascicles were spared. Predominant lesion focus was at a mean distance of 14.6 ± 5.4 cm proximal to the humeroradial joint. Discriminative power of quantitative T2 signal analysis and of qualitative lesion rating was high, with 100% sensitivity and 100% specificity (p < 0.0001). Fascicular T2 lesion patterns were rated as multifocal (n = 17), monofocal (n = 2), or indeterminate (n = 1) by 2 independent observers with strong agreement (kappa = 0.83). Conclusion: It has been difficult to prove the existence of fascicular/partial nerve lesions in spontaneous neuropathies using clinical and electrophysiologic findings. With MRN, fascicular lesions with strict somatotopic organization were observed in upper arm median nerve trunks of patients with AINS. Our data strongly support that AINS in the majority of cases is not a surgically treatable entrapment neuropathy but a multifocal mononeuropathy selectively involving, within the main trunk of the median nerve, the motor fascicles that continue distally to form the anterior interosseous nerve.

Stiff-man syndrome in a woman with breast cancer An uncommon central nervous system paraneoplastic syndrome

We report a patient who developed stiff-man syndrome, including disabling shoulder subluxation and wrist ankylosis, in association with breast cancer. Immunologic investigations disclosed autoimmunity directed against not only glutamic acid decarboxylase but also amphiphysin, a 128-kd protein located in the presynaptic compartment of neurons. The patient improved after surgery and corticosteroid treatment and has been stable for nearly 4 years on only anti-estrogenics. The triad of stiff-man syndrome, breast cancer, and autoantibodies against amphiphysin identifies a new autoimmune paraneoplastic syndrome of the CNS.

Inclusion body myositis presenting with isolated erector spinae paresis

Article abstract—We report a 70–year-old patient who presented with a 4–year history of weakness of paravertebral muscles. Electrodiagnostic studies revealed a mixed neurogenic-myopathic pattern. Light microscopic examination revealed atrophic fibers with rimmed vacuoles; electron microscopy demonstrated cytoplasmic and intranuclear filaments measuring about 16 nm in width, consistent with the diagnosis of inclusion body myositis. Therapy with corticosteroids provided only a mild and transient benefit. Ten months after the initial evaluation, clinical and electrodiagnostic examination demonstrated mild progression of the disease.

Homozygous mutations in caveolin-3 cause a severe form of rippling muscle disease

Heterozygous missense mutations in the caveolin‐3 gene (CAV3) cause different muscle disorders. Most patients with CAV3 alterations present with rippling muscle disease (RMD) characterized by signs of increased muscle irritability without muscle weakness. In some patients, CAV3 mutations underlie the progressive limb‐girdle muscular dystrophy type 1C (LGMD1C). Here, we report two unrelated patients with novel homozygous mutations (L86P and A92T) in CAV3. Both presented with a more severe clinical phenotype than usually seen in RMD. Immunohistochemical and immunoblot analyses of muscle biopsies showed a strong reduction of caveolin‐3 in both homozygous RMD patients similar to the findings in heterozygous RMD. Electron microscopy studies showed a nearly complete absence of caveolae in the sarcolemma in all RMD patients analyzed. Additional plasma membrane irregularities (small plasmalemmal discontinuities, subsarcolemmal vacuoles, abnormal papillary projections) were more pronounced in homozygous than in heterozygous RMD patients. A stronger activation of nitric oxide synthase was observed in both homozygous patients compared with heterozygous RMD. Like in LGMD1C, dysferlin immunoreactivity is reduced in RMD but more pronounced in homozygous as compared with heterozygous RMD. Thus, we further extend the phenotypic variability of muscle caveolinopathies by identification of a severe form of RMD associated with homozygous CAV3 mutations. Ann Neurol 2003

Meningeal Involvement in Wegener's Granulomatosis Confirmed and Monitored by Positive Circulating Antineutrophil Cytoplasm in Cerebrospinal Fluid

MRI and CSF investigations revealed meningeal involvement in a 29-year-old patient with biopsy-confirmed Wegeners granulomatosis. The intracranial manifestation of Wegeners granulomatosis was supported by the detection of pathologic circulating antineutrophil cytoplasm (c-ANCA) in the CSF. We monitored disease activity by c-ANCA measurement in the CSF. After repeated cycles of intrathecal administration of methotrexate and corticoids, progression of meningeal infiltration stopped, and CSF c-ANCA titers became negative. NEUROLOGY 1997;48: 263-265