Plasmapheresis decreases neuroelectric blocking activity in multiple sclerosis

Therapeutic plasma exchange for acute inflammatory demyelinating syndromes of the central nervous system

Idiopathic inflammatory demyelinating diseases (IIDDs) of the central nervous system, of which multiple sclerosis is the prototype, represent a family of monophasic, recurrent or progressive diseases with overlapping clinical and pathological manifestations. While most patients recover spontaneously or following a brief course of high-dose corticosteroids, occasional patients, particularly those with fulminant severe IIDDs, such as the Marburg variant, do not respond to corticosteroids and have severe, residual neurological deficits. While it is widely believed that IIDDs are mediated by T lymphocytes, as is experimental allergic encephelomyelitis, additional, possibly humoral, factors may be essential to generate the extensive demyelination seen in these conditions. Anecdotal reports over the past two decades have suggested that patients with acute, severe neurological deficits resulting from IIDDs, who fail to improve after high-dose intravenous corticosteroids, may benefit from plasma exchange. A randomized, sham-controlled, crossover study has recently been completed at the Mayo Clinic, which addresses these observations.

The pathophysiology of multiple sclerosis: the mechanisms underlying the production of symptoms and the natural history of the disease

The pathophysiology of multiple sclerosis is reviewed, with emphasis on the axonal conduction properties underlying the production of symptoms, and the course of the disease. The major cause of the negative symptoms during relapses (e.g. paralysis, blindness and numbness) is conduction block, caused largely by demyelination and inflammation, and possibly by defects in synaptic transmission and putative circulating blocking factors. Recovery from symptoms during remissions is due mainly to the restoration of axonal function, either by remyelination, the resolution of inflammation, or the restoration of conduction to axons which persist in the demyelinated state. Conduction in the latter axons shows a number of deficits, particularly with regard to the conduction of trains of impulses and these contribute to weakness and sensory problems. The mechanisms underlying the sensitivity of symptoms to changes in body temperature (Uhthoff's phenomenon) are discussed. The origin of 'positive' symptoms, such as tingling sensations, are described, including the generation of ectopic trains and bursts of impulses, ephaptic interactions between axons and/or neurons, the triggering of additional, spurious impulses by the transmission of normal impulses, the mechanosensitivity of axons underlying movement-induced sensations (e.g. Lhermitte's phenomenon) and pain. The clinical course of the disease is discussed, together with its relationship to the evolution of lesions as revealed by magnetic resonance imaging and spectroscopy. The earliest detectable event in the development of most new lesions is a breakdown of the blood-brain barrier in association with inflammation. Inflammation resolves after approximately one month, at which time there is an improvement in the symptoms. Demyelination occurs during the inflammatory phase of the lesion. An important mechanism determining persistent neurological deficit is axonal degeneration, although persistent conduction block arising from the failure of repair mechanisms probably also contributes.

Immunologically induced electrophysiological dysfunction: implications for inflammatory diseases of the CNS and PNS

During inflammation of the central or peripheral nervous system, a high number of immunologically active molecules, including bacterial or viral products as well as host-derived cytokines, are released. Patients suffering from inflammatory CNS or PNS diseases often develop transient symptoms with a rapid recovery, which obviously cannot be accounted for by immunologically induced tissue damage. These observations led to the hypothesis that immunologically active molecules can affect directly the electrophysiological functions of neurons and glial cells. Evidence for this hypothesis came from in vitro studies showing that cytokines, such as interleukins or tumor necrosis factors, arachidonic acid and its metabolites, interfere with electrophysiological properties of neurons or glial cells. These molecules affect ion currents, intracellular Ca2+ homeostasis, membrane potentials, and suppress or enhance the induction and maintenance of long-term potentiation. Similarly, virus proteins from human immunodeficiency virus type I were found to alter intracellular Ca2+ concentrations of neurons and astrocytes by modulating either transmitter receptors and channels or membrane transporters. Cerebrospinal fluid from MS patients contains factors which increase Na+ current inactivation and thereby reduce neuronal excitability. Immunoglobulins in sera of patients suffering from multifocal motor neuropathy and from acquired neuromyotonia interfere with nerve fibers, inducing alterations of conduction. Increased knowledge of these mechanisms will help to explain the pathogenesis of neurological symptoms and may provide a rationale for new therapeutic strategies.

Meta-analysis of clinical studies of the efficacy of plasma exchange in the treatment of chronic progressive multiple sclerosis

OBJECTIVE

To examine the hypothesis that addition of therapeutic plasma exchange (TPEX) to an immunosuppressive drug regimen increases that regimen's efficacy to halt the progression of chronic progressive multiple sclerosis (CPMS).

METHODS

The literature was searched for prospective controlled clinical trials evaluating the efficacy of TPEX in CPMS. Six studies were eligible for meta-analysis. Their results were combined, using Cochran's and Peto's methods. Three outcome measures were studied: 1) the change in Kurtzke's disability status scale (DSS) scores, 2) the relative odds of neurologic decline by 1 or more DSS grades, and 3) the relative odds of neurologic improvement by 1 or more DSS grades, in the treatment versus the comparison group of patients. Reported results of neurologic evaluations at 6, 12, 24, and 36 months of follow-up were analyzed separately.

RESULTS

TPEX significantly (P < .05) reduced the proportion of patients who experienced neurologic decline (by 1 or more DSS grades) at 12 months of follow-up (relative odds of decline = 0.441, 95% confidence interval = 0.210-0.929).

CONCLUSIONS

There is a need for further clinical research into the possibility of a beneficial effect of TPEX in patients with CPMS likely to experience neurologic decline over the ensuring 12 months. Targeting treatment to a particular subgroup of CPMS patients may be necessary for TPEX to prove effective.

Conduction properties of central demyelinated and remyelinated axons, and their relation to symptom production in demyelinating disorders

The conduction properties of central demyelinated and remyelinated axons are discussed, and related to the expression of symptoms in central demyelinating disease. The mechanisms underlying the block and restoration of conduction in segmentally demyelinated axons are described, together with the range of deficits expressed by the conducting axons. These abnormalities are related to clinical relapses and remissions, and to the phenomena of weakness, fatigue, the temperature sensitivity of symptoms, and the generation of 'positive' symptoms (e.g. Uhthoff's and Lhermitte's symptoms). The potential role of circulating 'blocking factors' in the symptomatology of central demyelinating disease is examined, and some approaches are advanced for the symptomatic therapy of such diseases.

Plasmapheresis in treatment of human T-lymphotropic virus type-I associated myelopathy

In 11 of 18 patients with human T-lymphotropic virus type-I (HTLV-I) associated myelopathy (HAM) gait, sensory, and/or sphincter disturbance improved with plasmapheresis (4 to 6 sessions in 2 weeks), and the effects were maintained for 2 to 4 weeks. Plasmapheresis lowered the titre of HTLV-I antibody in serum but not in cerebrospinal fluid, and change of HTLV-I antibody titres did not correlate with the effects of plasmapheresis. These results suggest that plasmapheresis is useful treatment, at least in producing a temporary improvement, in patients with HAM, and that some humoral factor(s), but not HTLV-I antibody, may be important in the pathogenesis of HAM.

Lymphocytoplasmapheresis in multiple sclerosis: one-year results in 6 patients

6 patients with definite MS underwent lymphocytoplasmapheresis for one year. Clinical data, evoked potential recordings and peripheral blood lymphocyte helper/suppressor ratio were assessed before and after the treatment and were compared with those of a control group of 10 multiple sclerosis patients. Lymphocytoplasmapheresis did not significantly modify clinical and laboratory findings compared with the control group.

Persistence of antibrain antibodies in cerebrospinal fluid during plasmapheresis for multiple sclerosis

A man with chronic progressive multiple sclerosis received a 10 day course of treatment with adrenocorticotrophic hormone without beneficial effect. He then received six sessions of plasmapheresis, again without improvement. Treatment with adrenocorticotrophic hormone had no effect on serum antibrain antibody titres, but plasmapheresis virtually eliminated the antibodies from serum and caused a fall in serum IgG concentrations; neither treatment had any effect on the IgG concentration and antibody titre in the cerebrospinal fluid. Treatment with plasmapheresis may fail in patients with multiple sclerosis because it does not remove antibrain antibodies from the intrathecal space.

Lymphocytoplasmapheresis in multiple sclerosis: preliminary laboratory findings

Short-term treatment with lymphocytoplasmapheresis was evaluated in 6 multiple sclerosis patients with special reference to the electrophysiological and immunological findings. Visual, somatosensory, brainstem auditory evoked potentials, flicker fusion test, helper/suppressor blood lymphocyte ratio, serum immunocomplexes and immunoglobulins and Kurtzke scores were evaluated in each patient before and after treatment. No statistically significant results were obtained.