Exome sequencing reveals a novel MRE11 mutation in a patient with progressive myoclonic ataxia

Progressive myoclonic ataxia (PMA) is a clinical syndrome defined as progressive ataxia and myoclonus and infrequent seizures in the absence of progressive dementia. Due to the extremely heterogeneous nature of PMA, a large proportion of PMA cases remain molecularly undiagnosed. The aim of this study was to clarify the molecular etiology of PMA. The patient was a 52-year-old female from consanguineous parents. She developed a jerking neck movement at age 9, which gradually expanded to her entire body. On physical examination at age 47, she exhibited generalized, spontaneous myoclonus that occurred continuously. She also presented with mild limb and truncal ataxia. An electroencephalogram revealed no abnormalities. A brain MRI displayed no atrophy of the cerebellum. Electrophysiological studies suggested myoclonus of a subcortical origin. For further evaluation, we performed exome sequencing, and we identified a novel homozygous missense mutation in the MRE11 gene (NM_005590:c.140C>T:p.A47V). Subsequently, we analyzed the expression of MRE11 and related proteins (RAD50 and NBS1) via Western blot, and they were markedly decreased compared to a healthy control. Mutations in the MRE11 gene have been known to cause an ataxia-telangiectasia-like (ATLD) disorder. Accumulating evidence has indicated that its wide phenotypic variations in ATLD correspond to genotypic differences. Interestingly, our case exhibited a relatively mild decrease in NBS1 compared to previously reported cases of a homozygous missense mutation, which may account for the milder phenotype in this patient. Moreover, together with a recently reported case of an MRE11 mutation, it is suggested that MRE11 mutations can present as PMA.

Clinical and imaging characterization of a patient with idiopathic progressive ataxia and palatal tremor

We describe clinical and imaging features of a patient with sporadic progressive ataxia and palatal tremor (PAPT) of unknown etiology. There was hypertrophy of bilateral inferior olivary nuclei with hyperintense T2-weighted signal and mild cerebellar atrophy at brain magnetic resonance imaging. 18F-fluoro-2-desoxy-d-glucose positron emission tomography scanning (FDG-PET) showed hypometabolism in the red nucleus, external globus pallidus and precuneus while FP-CIT-SPECT imaging revealed mild and progressive loss of striatal dopaminergic terminals. Our findings suggest that in idiopathic PAPT involvement of the dentato-rubro-olivary pathway occurs along with some dopaminergic dysfunction.

Acyclovir responsive brain stem disease after the Ramsay Hunt syndrome

We report an immunocompetent patient with the Ramsay Hunt syndrome (RHS) followed days later by brainstem disease. Extensive virological studies proved that varicella zoster virus (VZV) was the causative agent. Treatment with intravenous acyclovir resulted in prompt resolution of all neurological deficits except peripheral facial palsy. This case demonstrates that after geniculate zoster, brainstem disease may develop even in an immunocompetent individual and effective antiviral therapy can be curative.

DNA analysis in hereditary dentatorubral-pallidoluysian atrophy: correlation between CAG repeat length and phenotypic variation and the molecular basis of anticipation

Hereditary dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disease with variable clinical phenotypes. Progressive ataxia, choreoathetosis, and dementia are the main clinical features of adult-onset cases, whereas the main feature in juvenile-onset DRPLA is progressive myoclonus epilepsy. Earlier onset is apparent in successive generations (anticipation). The molecular abnormality underlying DRPLA is an expanded, unstable CAG trinucleotide repeat on chromosome 12p. We analyzed 71 DNA samples obtained from 12 Japanese DRPLA pedigrees that included 38 affected individuals. Normal alleles had 7 to 23 repeats, DRPLA alleles 53 to 88 repeats. DRPLA alleles also were detected in five asymptomatic family members. Patients with juvenile onset had significantly larger repeats than did those with adult onset, and there was a significant negative correlation between CAG repeat length and age at onset. In 80% of the paternal transmissions, there was an increase of more than five repeats, whereas all the maternal transmissions showed either a decrease or an increase of fewer than five repeats. There was a significant correlation between father-child differences in repeat length and differences in age at onset. The analysis of CAG repeat length is a reliable diagnostic test for DRPLA and is of value for the presymptomatic detection of individuals at risk. The expansion of CAG repeats is important in phenotypic variation and anticipation. In addition, the sex of the transmitting parent has a significant effect on the molecular mechanism of anticipation.

Ramsay Hunt syndrome: progressive mental deterioration in association with unusual cerebral white matter change

An autopsied case of Ramsay Hunt syndrome with progressive dementia was reported. The clinical symptoms included progressive intellectual decline, myoclonus, generalized convulsive seizure, cerebellar ataxia and positive pyramidal signs. Neuropathological examination disclosed cerebral white matter demyelination marked in the frontal lobe and fibrillary gliosis predominantly in the subcortical U-fibers, grumose degeneration in the dentate nucleus and inferior olivary nucleus lesion. The skeletal muscle showed no ragged-red fiber. The present case can be included in Ramsay Hunt syndrome because of the absence of pathological hallmark of mitochondrial encephalomyopathy and of the presence of the degenerative lesions in the olivary and dentate nucleus without cerebellar Purkinje cell loss. The intellectual decline is a result of extensive frontal white matter change, and myoclonus and ataxia are closely associated with dentate grumose degeneration. The cerebral white matter change is an unusual finding and the present case might be a variant in Ramsay Hunt syndrome.

Progressive myoclonus epilepsies: an electroclinical, biochemical, morphological and molecular genetic study of 17 cases

Electroclinical, morphological, biochemical and molecular genetic data from 17 patients affected by progressive myoclonus epilepsies (PME) are reported. Twelve patients were characterized by prominent action myoclonus, sporadic seizures, mild ataxia, lack of dementia and persistence of normal EEG background activity; three patients showed a more rapid worsening of symptomatology, characterized by early mental impairment, massive and action myoclonus, cerebellar signs and tonic clonic seizures; in these patients EEG background activity was slow, even in early stages of the disease. In two patients, previously classified as cryptogenetic PME, a mitochondrial aetiology was recognized by the presence of ragged red fibers in muscle biopsy and by a reduction of the respiratory chains enzymes. Molecular genetical investigation of mtDNA demonstrated the reported heteroplasmic point mutation at nt 8344 of mtDNA in the two MERRF patients, while it was negative in all of the others.

Dyssynergia cerebellaris myoclonica (Ramsay Hunt syndrome): a condition unrelated to mitochondrial encephalomyopathies

Thirteen patients with dyssynergia cerebellaris myoclonica (Ramsay Hunt syndrome) had full clinical and neurophysiological study as well as muscle biopsy. The patients had action myoclonus, generalised epileptic seizures, and mild cerebellar syndrome. The disease was inherited in an autosomal recessive pattern in five patients, and occurred as isolated cases in the remaining eight patients. The age at onset of symptoms ranged from 6 to 15 years (mean, 10.4 years). The EEG and polygraphic findings included normal background activity in most patients, spontaneous fast generalised spike-and-wave discharges, photosensitivity, no activation during slow sleep, and vertex and rolandic spikes in REM sleep. Results of muscle biopsy, performed an average of 14 years after onset of the disease, were normal and showed no mitochondrial abnormalities. These findings suggest that Ramsay Hunt syndrome is a condition with distinctive clinical and neurophysiological features and unrelated to mitochondrial encephalomyopathies.

Normal muscle mitochondrial function in Ramsay-Hunt syndrome

Mitochondrial encephalomyopathies may display clinical features similar to Ramsay-Hunt syndrome (RHS). We studied muscles mitochondrial function in 2 patients with RHS. Histochemical and ultrastructural studies of muscle biopsies and biochemical analysis of muscle mitochondrial enzymes were normal. There is no evidence for a disturbance of muscle mitochondrial function in RHS.

Cerebellar efferent fibers around the dentate nucleus. Pathological anatomy in olivo-ponto-cerebellar and dentato-pallido-luysian atrophy

In patients with olivo-ponto-cerebellar atrophy (OPCA), the deep cerebellar white matter showed evidence of severe degeneration and gliosis. However, the circumferential white matter enclosing the dentate nucleus was less involved. In addition, the Holzer stain verified the presence of mild gliosis inside the wrinkled band of the dentate gray matter. In contrast, dentato-rubro-pallido-luysian atrophy (DRPLA) affected the mantle layer covering the dentate nucleus. The fibers encircling the dentate nucleus, which degenerate in DRPLA and are spared in OPCA, are anatomically noticeable to be dentatofugal pathways. Moreover, the afferent fibers from the cerebellar cortex and other systems may reach the dentate nucleus partly from the medial aspect via the hilus, as was noted in cases of OPCA.

Ramsay Hunt syndrome in dentatorubral-pallidoluysian atrophy

We report a case of Ramsay Hunt syndrome which was clinically characterized by myoclonus epilepsy, cerebellar ataxia, convulsions, and dementia. Major necropsy findings were dentatorubral-pallidoluysian atrophy. Dentatorubral-pallidoluysian atrophy may be associated with a variety of clinical symptoms, amongst which Ramsay Hunt syndrome can be included.

Progressive myoclonus and epilepsy with dentatorubral degeneration: a clinicopathological study of the Ramsay Hunt syndrome

Ramsay Hunt's progressive myoclonus and epilepsy associated with dentatorubral degeneration is a rare disorder. We report a 19 year old woman with this clinical syndrome who also has a more mildly affected brother. Neuropathological in addition to dentatorubal involvement. The evidence suggests that this is a distinctive hereditary disorder producing neuromal degeneration at several levels in the central nervous system.

[Familial olivo-ponto-cerebellar atrophy with myoclonus. Limits of cerebellar myoclonic dyssynergia (Ramsay-Hunt syndrome)]

The case is described of a woman of 26 suffering (like her mother, a brother and a sister) from a progressively degenerating cerebellar syndrome, at first considered to be hereditary cerebellar ataxia, but which, after action myoclonus appeared, was diagnosed as dyssynergia cerebellaris myoclonica (D.C.M.). Anatomical verification however revealed a syndrome of olivo-ponto-cerebellar atrophy comprising massive demyelinisation of the white matter of the cerebellum and of the cerebellopontine fibres; atrophy of the pontine nuclei; the cerebellar cortex itself was severely affected; moderate nigral lesions; marked spinal lesions of the cerebellospinal fasciculi and of the posterior columns; lesions of the anterior horns and of the bulbar nuclei; cortical chromatolysis. The fact that the dentate system remained unaffected, also noted in some cases of olivo-ponto-cerebellar atrophy with myoclonus, whilst in a number of other cases the lesion remains clinically silent, emphasises the difficulty in establishing an accurate correlation between myoclonus and dentate nucleus. Discussion of the nosological limits of D.C.M.: confirmed cases generally displayed lesions of the dentate system and hereditary degenerative spino-cerebellar lesions. The same clinical symptoms can be observed in cases which do not come under this classification--or even under that of degenerative conditions of the cerebellar system--and D.C.M. appears to be only a syndrome, the Ramsay-Hunt syndrome.