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Takahashi et al. found autoantibodies against the NMDA-type GluR epsilon2 in patients with chronic epilepsia partialis continua, including patients with proven or clinically suspected Rasmussen’s encephalitis, with an acute encephalitis or encephalopathy, and with nonprogressive epilepsia partialis continua. Antibodies were predominantly against cytoplasmic (C-terminal) epitopes but antibody profiles did not show consistent changes during the course of disease. The data suggest that cytotoxic T-cell-mediated neuronal damage occurs in these conditions.
see page 891
Intractable seizures: T cells vs antibodies
Commentary by Robert A. Gross, MD, PhD
Researchers seeking the basis for Rasmussen’s encephalitis (RE) were galvanized by a report1 of excitatory antibodies to the glutamate receptor GluR3, and the successful treatment of a patient with plasma exchange. Was excessive excitation the cause of the debilitating seizures and would immunotherapy therefore be effective?2 The evidence for an autoimmune basis of RE is sound—involving both B- and T-cell-mediated processes—but was tempered by reports that some patients were seronegative for gluR3 antibodies.3,4 The root cause, the identity of the antigens against which antibodies reacted, and whether they were causative of pharmacoresistant seizures thus remained in some doubt.
In this issue, Takahashi et al. tested the hypothesis that T-cell-mediated immunity plays a role in the pathogenesis of RE and its seizures. To do this, they compared GluR epsilon2 subunit antibodies in serum and CSF in patients with epilepsia partialis continua (EPC) (some with RE), patients with other causes of intractable seizures (West and Lennox-Gastaut syndromes), and controls. They found that GluR epsilon2 antibodies were present only in patients with EPC, antibodies were directed primarily against cytoplasmic epitopes (suggesting T-cell-mediated immunity), and the number of targeted epitopes increased during progression in some patients. They therefore concur with other investigators that in RE antibodies may exist against numerous antigens, but suggest further that although these antibodies could be the cause of debilitating seizures in RE (but not for other typically pharmacoresistant seizure syndromes), the antibodies are made after T-cell-mediated damage. As we await the definitive elucidation of cause and effect, the evidence in this carefully done study both expands and refines our view of the pathogenesis of seizures in RE.
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see page 891
mtDNA replicative infidelity due to POLG1 mutations
Del Bo et al. analyzed mitochondrial DNA (mtDNA) from muscle tissue of patients with mtDNA multiple deletions syndromes. The accumulation of a high level of mtDNA point mutations in subjects carrying specific POLG1 gene mutations points to a relevant pathogenetic mechanism in this PEO subgroup.
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see page 903
In the accompanying editorial, Patrick Chinnery reviews recent developments in the understanding of nuclear genetic disorders that cause secondary mtDNA damage. There is emerging evidence that subtle differences at the molecular level have important pathophysiologic consequences, possibly explaining the clinical variation between different disorders of mtDNA maintenance and opening new avenues for treatment.
see page 878
DBS improves essential tremor
Vaillancourt et al. demonstrate that deep brain stimulation (DBS) of the ventral intermediate nucleus of the thalamus increased tremor frequency while reducing the amplitude, regularity, and tremor-EMG coherence.
see page 919
Analgesic effects of botulinum toxin A
Voller et al. found no direct analgesic effect of botulinum toxin A on the skin of 16 subjects using three different pain models. Their work implies that botulinum toxin A reduces pain mainly by its effects on muscle tone.
see page 940
Adjusting anticoagulation for endoscopy: The stroke risk
Anticoagulated patients undergoing invasive procedures often pose a management dilemma. Blacker et al. studied 987 patients with atrial fibrillation (with and without valvular lesions) undergoing 1,137 procedures to determine the stroke risk when anticoagulation was adjusted for endoscopies. They identified factors associated with a high risk, including age >80 years, hypertension, and hyperlipidemia.
see page 964
Rehabilitation therapy and corticospinal excitability
In a group of patients with chronic poststroke agraphia, aphasia, and right hemiparesis, Papathanasiou et al. found increased recruitment of corticospinal pathways following a session of prosthesis-aided rehabilitation therapy of writing. Their results suggest that, even in chronic, poorly recovered poststroke patients, rehabilitation therapy aimed at increased use of the paretic hand may induce reorganization of corticospinal pathways.
see page 977
Induction of plastic change in motor cortex after stroke
Uy et al. employed paired TMS and nerve stimulation to induce motor cortical plasticity in patients with stroke with chronic hemiplegia. Some improvement in neurophysiologic and function measures were seen, but the results were inconsistent.
see page 982
The editorial by Felix M. Mottaghy accompanying these two articles reviews the possible mechanism for these intriguing effects of rehabilitation but concludes that this promising technique and its sophisticated rehabilitation concepts need to be tested in a larger number of patients with suitable controls, stratifying patients based on lesion site and degree of disability.
see page 881
Orthostatic headaches caused by postural tachycardia syndrome
Mokri and Low report four patients with postural tachycardia syndrome who presented with orthostatic headaches. Not all cases of orthostatic headaches result from intracranial hypotension or CSF leaks. Occasionally orthostatic headaches may be the dominant clinical manifestations of postural tachycardia syndrome.
see page 980
HD-like 2 and chorea-acanthocytosis
Walker et al. report that affected members of a family originally reported as autosomal dominant chorea-acanthocytosis were found to carry the trinucleotide repeat expansion associated with Huntington disease-like 2.
see page 1002
L-Dopa can induce daytime sleepiness in PD
Garcia-Borreguero et al. describe a double-blind, placebo-controlled study of a 74-year-old patient complaining of drug-induced daytime sleepiness. Administration of L-dopa increased daytime sleepiness documented by multiple sleep latency tests. Thus daytime sleepiness is not restricted to dopamine agonists.
see page 1008
References
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