Motor neuron dysfunctions in the frontotemporal lobar degeneration spectrum: a clinical and neurophysiological study.

BACKGROUND: Although only a few frontotemporal lobar degeneration (FTLD) patients develop frank amyotrophic lateral sclerosis (ALS), motor neuron dysfunctions (MNDys) occur in a larger proportion of patients. The aim of this study is to evaluate MNDys and ALS in a sample of consecutively enrolled sporadic FTLD patients. METHODS: Clinical and neurophysiological evaluations (i.e. needle electromyography) assessed lower (LMN) and upper (UMN) motor neuron function at the baseline in 70 probable FTLD patients (i.e., 26 behavioural variant-bvFTD, 20 primary progressive aphasias-PPAs and 24 corticobasal syndrome-CBS). To obtain a more accurate estimation, quantitative scales were also applied (i.e. ALSFRS-r and UMN scale). Patients were screened for MAPT, GRN and C9orf72 mutations. A mean clinical follow-up of 27.8±22.4 months assessed MNDys progression and the clinical presentation of ALS. RESULTS: Five genetic cases were identified. Within the sample of sporadic patients, a relative low rate of FTLD patients was diagnosed as probable ALS (5%), while a higher proportion of patients (17%) showed clinical and neurophysiological MNDys. Thirteen patients (20%) presented with isolated clinical signs of LMN and/or UMN dysfunction, and 8 patients (12%) showed neurogenic changes at the electromyography. No differences in FTLD phenotype and disease duration were found between MNDys positive and negative patients. Clinical MNDys were highly associated with positive electromyographic findings. At follow-up, no MNDys positive patient developed ALS. CONCLUSION: Neurophysiological and clinical examinations revealed mild MNDys in FTLD patients not fulfilling criteria for ALS. This condition did not evolve at a mean follow-up of two years. These results, indicating a subclinical degeneration of corticospinal tracts and lower motor neurons, suggest that FTLD patients may be more at risk of MNDys than the general population.

Analysis of mtDNA deletions in muscle by in situ hybridization.

We compared the distribution of deleted mitochondrial DNA (Delta-mtDNA) in skeletal muscle of a patient with autosomal recessive (AR) and another with autosomal dominant (AD) progressive external ophthalmoplegia (PEO) by in situ hybridization (ISH). The patients studied had similar numbers of fibers deficient in cytochrome c oxidase (COX) activity (13.6% and 12.8%) and fibers with mitochondrial proliferation (5.5% and 5.3%). ISH suggested that each COX-deficient fiber contained a single species of Delta-mtDNA. Most deletions ablated the region between the genes encoding adenosine triphosphate (ATP) synthase subunit 8 and cytochrome b. Fibers that appeared to be depleted of mtDNA were also present. We conclude that muscle from patients with autosomally inherited PEO contains not only Delta-mtDNA but also focal depletion of mtDNA and that the distribution of these mtDNA defects appears to be similar. These changes most likely represent the common consequence of whatever genetic factors are responsible for the generation of Delta-mtDNA.

Central nervous system superficial siderosis, headache, and epilepsy.

Almost 95 cases of superficial siderosis of the central nervous system have been reported in the literature. These patients showed a clinical syndrome characterized by ataxia, deafness, pyramidal system involvement, and mental deterioration with xanthochromic cerebrospinal fluid and neuroradiological findings of hemosiderin deposits. About 30% of the patients had headache as an accompanying symptom. In the present case report, we describe a 33-year-old man with the typical clinical features of superficial siderosis, who complained, since aged 8, of a severe recurrent frontal headache often associated with loss of consciousness occurring after at least 2 hours of pain. The MRI and CSF findings were consistent with subarachnoid bleeding. In our patient, headache due to meningeal irritation by subarachnoid blood induced seizures as a probable reflex of extreme pain. Carbamazepine and nimodipine prophylaxis dramatically reduced the frequency of headaches and seizures.

Multiple mitochondrial DNA deletions in sporadic inclusion body myositis: a study of 56 patients.

Inclusion body myositis, a chronic inflammatory disorder, is the most common cause of myopathy in adults over the age of 50. Diagnosis is based on clinical features and distinctive morphological findings by both light and electron microscopy. The causes of inclusion body myositis are still unknown. Ultrastructural mitochondrial changes and ragged-red fibers are common in patients with sporadic inclusion body myositis, and multiple [correction of mutiple] mitochondrial DNA (mtDNA) deletions have been reported in 3 such patients, suggesting that mtDNA mutations may have a pathogenetic role. We studied 56 patients with sporadic inclusion body myositis, using a combination of clinical, morphological, biochemical, and molecular genetic analyses to determine the frequency and the distribution of mtDNA deletions. Using the polymerase chain reaction, we found multiple mtDNA deletions in 73% of patients, compared to 40% of normal age-matched control subjects and 47% of disease control subjects. The presence of deletions correlated with morphological evidence of ragged-red, cytochrome c oxidase-negative fibers, and with defects of complexes I and IV of the electron transport chain. Although aging may account for a proportion of mtDNA deletions in patients with sporadic inclusion body myositis and control subjects, mtDNA alterations may be accelerated in sporadic inclusion body myositis.