Peripheral nerve involvement in hereditary cerebellar and multisystem degenerative disorders

Neuropathy in ARSACS is demyelinating but without typical nerve enlargement in nerve ultrasound

BACKGROUND

To specify peripheral nerve affection in autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) by correlating high-resolution nerve ultrasound and nerve conduction studies.

METHODS

We assessed a cohort of 11 ARSACS patients with standardized nerve conduction studies and high-resolution ultrasound of peripheral nerves and compared nerve ultrasound findings to a healthy control group matched for age, sex, size and weight.

RESULTS

Mean age of patients was 39.0 (± 14.1) years and disease duration at assessment 30.6 (± 12.5) years. All patients presented with a spasticity, ataxia and peripheral neuropathy. Neuropathy appeared to be primarily demyelinating in 9/11 cases and was not classifiable in 2/11 cases due to not evocable potentials. Nerve ultrasound revealed a normal ultrasound pattern sum score (UPSS) in each ARSACS patient and no significant nerve enlargement compared to the control group.

CONCLUSIONS

Peripheral neuropathy in ARSACS showed primarily demyelinating rather than axonal characteristics and presented without nerve enlargement. As demyelinating neuropathies do commonly present enlarged nerves we recommend further genetic testing of the SACS gene in patients who present with this combination of demyelinating neuropathy without nerve enlargement. ARSACS cases that initially presented only with neuropathy without spasticity or ataxia and therefore were misdiagnosed as Charcot-Marie-Tooth disease are supporting this suggestion.

History of Ataxias and Paraplegias with an Annotation on the First Description of Striatonigral Degeneration

The aim of this paper is to carry out a historical overview of the evolution of the knowledge on degenerative cerebellar disorders and hereditary spastic paraplegias, over the last century and a half. Original descriptions of the main pathological subtypes, including Friedreich's ataxia, hereditary spastic paraplegia, olivopontocerebellar atrophy and cortical cerebellar atrophy, are revised. Special attention is given to the first accurate description of striatonigral degeneration by Hans Joachim Scherer, his personal and scientific trajectory being clarified. Pathological classifications of ataxia are critically analysed. The current clinical-genetic classification of ataxia is updated by taking into account recent molecular discoveries. We conclude that there has been an enormous progress in the knowledge of the nosology of hereditary ataxias and paraplegias, currently encompassing around 200 genetic subtypes.

Cutaneous and muscular afferents from the foot and sensory fusion processing: Physiology and pathology in neuropathies

The foot-sole cutaneous receptors (section 2), their function in stance control (sway minimisation, exploratory role) (2.1), and the modulation of their effects by gait pattern and intended behaviour (2.2) are reviewed. Experimental manipulations (anaesthesia, temperature) (2.3 and 2.4) have shown that information from foot sole has widespread influence on balance. Foot-sole stimulation (2.5) appears to be a promising approach for rehabilitation. Proprioceptive information (3) has a pre-eminent role in balance and gait. Reflex responses to balance perturbations are produced by both leg and foot muscle stretch (3.1) and show complex interactions with skin input at both spinal and supra-spinal levels (3.2), where sensory feedback is modulated by posture, locomotion and vision. Other muscles, notably of neck and trunk, contribute to kinaesthesia and sense of orientation in space (3.3). The effects of age-related decline of afferent input are variable under different foot-contact and visual conditions (3.4). Muscle force diminishes with age and sarcopenia, affecting intrinsic foot muscles relaying relevant feedback (3.5). In neuropathy (4), reduction in cutaneous sensation accompanies the diminished density of viable receptors (4.1). Loss of foot-sole input goes along with large-fibre dysfunction in intrinsic foot muscles. Diabetic patients have an elevated risk of falling, and vision and vestibular compensation strategies may be inadequate (4.2). From Charcot-Marie-Tooth 1A disease (4.3) we have become aware of the role of spindle group II fibres and of the anatomical feet conditions in balance control. Lastly (5) we touch on the effects of nerve stimulation onto cortical and spinal excitability, which may participate in plasticity processes, and on exercise interventions to reduce the impact of neuropathy.

Clinical and neuroradiological features of spinocerebellar ataxia 38 (SCA38)

INTRODUCTION

SCA38 (MIM 611805) caused by mutations within the ELOVL5 gene, which encodes an enzyme involved in the synthesis of long-chain fatty acids with a high and specific expression in Purkinje cells, has recently been identified.

OBJECTIVE

The present study was aimed at describing the clinical and neuroimaging features, and the natural history of SCA38.

METHODS

We extended our clinical and brain neuroimaging data on SCA38 including 21 cases from three Italian families. All had the ELOVL5 c.689G > T (p.Gly230Val) missense mutation.

RESULTS

Age at disease onset was in the fourth decade of life. The presenting features were nystagmus (100% of cases) and slowly progressive gait ataxia (95%). Frequent signs and symptoms included pes cavus (82%) and hyposmia (76%); rarer symptoms were hearing loss (33%) and anxiety disorder (33%). The disease progressed with cerebellar symptoms such as limb ataxia, dysarthria, dysphagia, and ophtalmoparesis followed in the later stages by ophtalmoplegia. Peripheral nervous system involvement was present in the last phase of disease with sensory loss. Dementia or extrapyramidal signs were not detected. Significant loss of abilities of daily living was reported only after 20 years of the disease. Brain imaging documented cerebellar atrophy with sparing of cerebral cortex and no white matter disease.

CONCLUSIONS

SCA38 is a rare form of inherited ataxia with characteristic clinical features, including pes cavus and hyposmia, that may guide genetic screening and prompt diagnosis in light of possible future therapeutic interventions.

Ataxia of Charlevoix-Saguenay: MR and Clinical Results in Lower-Limb Musculature

OBJECTIVE

Peripheral neuropathy is a cardinal manifestation of the autosomal recessive spastic ataxia of Charlevoix- Saguenay (ARSACS), although its type of neuromuscular involvement has not been definitely established, and magnetic resonance imaging (MRI) plays an important role in the assessment of muscle and nerve diseases. The objective of this work has been to define the patterns of muscle weakness and of abnormal muscular MRI in ARSACS.

PATIENTS AND METHODS

Five patients with a molecular diagnosis of ARSACS, aged 39 to 59 years, whose electrophysiological findings were consistent with an axonal neuropathy of distal distribution superimposed on a developmental defect of myelinization, underwent neurological and MRI lower-limb examinations. Conventional FSE T1-weighted and STIR sequences were performed, looking for fatty infiltration and oedema in the musculature of the thighs, legs and feet, together with their distribution along the longitudinal axis of the muscle bellies.

RESULTS

On clinical examination, paralysis was apparent in foot muscles; moderate weakness, in leg musculature; and normal strength, in thigh muscles. MRI demonstrated massive fat deposition in the foot muscles and medial gastrocnemii in every case, distal fat infiltration and oedema in every leg muscle group, and preservation of thigh muscles, albeit with diffuse minimal non-specific fat infiltration. An inverse correlation between strength and degree of fat infiltration in lower-limb muscles became apparent.

CONCLUSION

The preponderance of weakness and MRI abnormalities in distal muscle groups was concordant with the presence of a length-dependent axonopathy, as described in ARSACS.

Ataxie de Charlevoix-Saguenay : IRM et observations cliniques au niveau de la musculature des membres inférieurs.