Lucio Santoro

Human mitochondrial DNA deletions associated with mutations in the gene encoding Twinkle, a phage T7 gene 4-like protein localized in mitochondria

The gene products involved in mammalian mitochondrial DNA (mtDNA) maintenance and organization remain largely unknown. We report here a novel mitochondrial protein, Twinkle, with structural similarity to phage T7 gene 4 primase/helicase and other hexameric ring helicases. Twinkle colocalizes with mtDNA in mitochondrial nucleoids. Screening of the gene encoding Twinkle in individuals with autosomal dominant progressive external ophthalmoplegia (adPEO), associated with multiple mtDNA deletions, identified 11 different coding-region mutations co-segregating with the disorder in 12 adPEO pedigrees of various ethnic origins. The mutations cluster in a region of the protein proposed to be involved in subunit interactions. The function of Twinkle is inferred to be critical for lifetime maintenance of human mtDNA integrity.

Sensory deficit in Parkinson's disease: evidence of a cutaneous denervation

Sensory disturbances are part of the clinical picture of Parkinsons disease. Abnormalities in sensory processing, through a basal ganglia involvement, are thought to be responsible for the sensory dysfunction since sensory nerve conduction velocity (NCV) is usually normal. However, NCV does not examine small fibres or terminal endings of large sensory fibres, whereas skin biopsy is more suitable for these purposes. To evaluate peripheral sensory nerves in Parkinsons disease, we studied cutaneous free and encapsulated sensory nerve endings in 18 patients and 30 healthy controls using 3-mm punch biopsies from glabrous and hairy skin. Ten patients had additional skin biopsies from the contralateral side. Further evaluation included NCV and Quantitative Sensory Testing. Parkinsons disease patients showed a significant increase in tactile and thermal thresholds (P < 0.01), a significant reduction in mechanical pain perception (P < 0.01) and significant loss of epidermal nerve fibres (ENFs) and Meissner corpuscles (MCs) (P < 0.01). In patients with bilateral biopsies, loss of pain perception and ENFs was higher on the more affected side (P < 0.01). We found evidence suggesting attempts at counteracting degenerative processes as increased branching, sprouting of nerves and enlargement of the vascular bed. Morphological and functional findings did not correlate with age or disease duration. Disease severity correlated with loss of MCs and reduction in cold perception and pain perception. We demonstrated a peripheral deafferentation in Parkinsons disease that could play a major role in the pathogenesis of the sensory dysfunction.

Ascorbic acid in Charcot-Marie-Tooth disease type 1A (CMT-TRIAAL and CMT-TRAUK): a double-blind randomised trial

Summary Background Ascorbic acid reduced the severity of neuropathy in transgenic mice overexpressing peripheral myelin protein 22 (PMP22), a model of Charcot–Marie–Tooth disease type 1A (CMT1A) associated with the PMP22 duplication. However, in three 1-year trials, ascorbic acid had no benefit in human beings. We did a multicentre 2-year trial to test the efficacy and tolerability of ascorbic acid in patients with CMT1A. Methods Adult patients (aged 18–70 years) with symptomatic CMT1A were enrolled from nine centres in Italy and the UK, and were randomly assigned (1:1 ratio) to receive 1·5 g/day oral ascorbic acid or matching placebo for 24 months. The randomisation sequence was computer generated by block randomisation, stratified by centre and disease severity, and patients were allocated to treatment by telephone. The primary outcome was change in the CMT neuropathy score (CMTNS) at 24 months. Secondary outcomes were timed 10 m walk test, nine-hole peg test, overall neuropathy limitations scale, distal maximal voluntary isometric contraction, visual analogue scales for pain and fatigue, 36-item short-form questionnaire, and electrophysiological measurements. Patients, treating physicians, and physicians assessing outcome measures were masked to treatment allocation. Analysis of the primary outcome was done on all randomised patients who received at least one dose of study drug. This study is registered, numbers ISRCTN61074476 (CMT-TRAUK) and EudraCT 2006-000032-27 (CMT-TRIAAL). Findings We enrolled and randomly assigned 277 patients, of whom six (four assigned to receive ascorbic acid) withdrew consent before receiving treatment; 138 receiving ascorbic acid and 133 receiving placebo were eligible for analysis. Treatment was well tolerated: 241 of 271 patients (89% in each group) completed the study; 20 patients (nine receiving ascorbic acid) dropped out because of adverse events. Mean CMTNS at baseline with missing data imputed was 14·7 (SD 4·8) in the ascorbic acid group and 13·9 (4·2) in the placebo group. Mean worsening of CMTNS was 0·2 (SD 2·8, 95% CI −0·3 to 0·7) in the ascorbic acid group and 0·2 (2·7, −0·2 to 0·7) in the placebo group (mean difference 0·0, 95% CI −0·6 to 0·7; p=0·93). We recorded no differences between the groups for the secondary outcomes at 24 months. 21 serious adverse events occurred in 20 patients, eight in the ascorbic acid group and 13 in the placebo group. Interpretation Ascorbic acid supplementation had no significant effect on neuropathy compared with placebo after 2 years, suggesting that no evidence is available to support treatment with ascorbic acid in adults with CMT1A. Funding Telethon-UILDM and AIFA (Italian Medicines Agency) for CMT-TRIAAL, and Muscular Dystrophy Campaign for CMT-TRAUK.

Late recovery after traumatic, anoxic, or hemorrhagic long-lasting vegetative state

Objectives: Late recovery of awareness in vegetative state (VS) is considered as an exceptional outcome, and has been reported prevalently after traumatic brain injury (TBI). The present prospective study aimed to verify frequency of late recovery (later than 1 year postonset in TBI and 3 months postonset in patients without TBI) of responsiveness and consciousness in traumatic and nontraumatic long-lasting (more than 6 months after onset) VS. Methods: Fifty inpatients with long-lasting VS (36% TBI, 36% hemorrhagic, and 28% anoxic) were enrolled and followed up for a mean of 25.7 months from onset (5 patients for more than 4 years). Level of responsiveness and functional disability were evaluated by means of validated scales (Coma Recovery Scale–Revised and Disability Rating Scale). Results: At the end of the study, 21 patients (42%) had died, 17 patients (34%) were in VS, and 2 patients with TBI (4%) had recovered responsiveness within 12 months postonset. The remaining 10 (20%) patients with TBI and patients without TBI showed late recovery of responsiveness; 6 of them (12%) further progressed to consciousness. Late recovery was significantly associated with younger age and was relatively more frequent in TBI. Functional abilities were severely impaired in all patients. Conclusions: This clinical study demonstrates that late recovery of responsiveness and consciousness is not exceptional in patients with traumatic and nontraumatic VS, although with residual severe disability.

Quantification of myelinated endings and mechanoreceptors in human digital skin

We used immunohistochemistry and confocal microscopy applied to fingertip punch biopsy to study glabrous skin innervation in 14 healthy subjects. In addition to epidermal nerve fibers, we quantified mechanoreceptors and their myelinated afferents. Using digital images and dedicated software, we calculated caliber, internodal and nodal length, and G‐ratio of the last four internodes of the myelinated endings. In our skin samples, we found a mean density of 59.0 ± 29.3 myelinated endings per square millimeter with a mean diameter of 3.3 ± 0.5μm and an internodal length of 79.1 ± 13.8μm. These findings indicate that Aβ fibers undergo drastic changes in their course from the nerve trunk to the target organ, with repeated branching and consequent tapering and shortening of internodal length. Our work demonstrates that skin biopsy can give information on the status of large myelinated endings as well as unmyelinated sensory and autonomic nerves. Since distal endings are primarily involved in distal axonopathy, skin biopsy can be more suitable than sural nerve biopsy to detect early abnormalities. In addition to diagnostic applications, this technique allows clarification of the mode of termination of Aβ fibers and their relationship with mechanoreceptors, leading to relevant electrophysiological speculations. Ann Neurol 2003

Absent innervation of skin and sweat glands in congenital insensitivity to pain with anhidrosis

OBJECTIVES A case of a 10-year-old girl with congenital insensitivity to pain with anhidrosis (CIPA) is reported. METHODS AND RESULTS Parents referred several hyperpyretic episodes without sweating occurring since birth, and insensitivity to pain, noticed when the child was 2 years old. Her body had many bruises and scars, bone fractures and signs of self-mutilation. Neurological examination was normal except for insensitivity to pain. Her IQ was 52. Electrical and tactile sensory nerve conduction velocities were normal. The patient was unable to detect thermal stimuli. Histamine injection evoked a wheal but not a flare; pilocarpine by iontophoresis did not induce sweat. Microneurography showed neural activity from A-beta sensory fibers while nociceptive and skin sympathetic C fiber nerve activity was absent. No small myelinated fibers and very rare unmyelinated fibers were found in the sural nerve. Immunohistochemistry showed a lack of nerve fibers in the epidermis and only few hypotrophic and uninnervated sweat glands in the dermis. CONCLUSIONS The lack of innervation of the skin (C and A-delta fibers) appears to be the morphological basis of insensitivity to pain and anhidrosis, and is consistent with the loss of unmyelinated and small myelinated fibers in the sural nerve biopsy.

Myelinated nerve endings in human skin

We used immunohistochemical techniques and confocal microscopy to study the morphometry of myelinated nerve endings in glabrous and hairy skin. A total of 30 healthy volunteers took part in this study designed to assess the possibility of obtaining reliable information on myelinated fibers using samples of hairy skin and to determine whether differences exist between myelinated terminations from different sites. We obtained consistent information on cutaneous myelinated terminations using hairy as well as glabrous skin samples. Myelinated endings from hairy and glabrous skin differ in density and distribution. However, from a comparison of our findings with data from nerve biopsy studies, we conclude that all cutaneous myelinated terminations are thinner terminal branches of large myelinated Aβ fibers, whereas cutaneous terminations of small myelinated Aδ fibers lose their myelin before entering the dermis and become indistinguishable from C‐fiber terminations. The classic criteria, based on fiber size, used to distinguish myelinated fiber subgroups in sensory nerves are therefore not suitable for identifying myelinated terminations in the skin. Muscle Nerve, 2007

Possible risk factors for primary adult onset dystonia: a case-control investigation by the Italian Movement Disorders Study Group

OBJECTIVES Little is known about the aetiology of idiopathic adult onset dystonia. The Italian Movement Disorders Study Group promoted a case-control study on some hypothetical risk factors including past medical events, life events, life habits, occupational hazards, and family hystory of dystonia, parkinsonism, and tremor. METHODS Cases affected by idiopathic adult onset dystonia (age at symptom onset >20 years, duration of disease >one year and <five years) were selected among consecutive outpatients attending 14 Italian centres. Control outpatients matched for age (±5 years), sex, and referral centre were identified among diagnostic categories thought to be unassociated with study exposures. Information was obtained by a standardised questionnaire administered by medical interviewers. Conditional logistic univariate and multivariate regression analyses were performed by a standard statistical package. RESULTS Multivariate analysis on 202 cases and 202 age and sex matched control outpatients indicated that head or facial trauma with loss of consciousness, family history of dystonia, and family history of postural tremor independently increased the risk of developing adult onset dystonia, whereas hypertension and cigarette smoking exerted a protective effect. The findings also suggested a positive association between local body injury—for example, previous ocular diseases and neck or trunk trauma—and dystonia of the same body part. CONCLUSIONS The results support the idea that environmental and genetic factors may both be important in the aetiology of adult onset dystonia, and suggest aetiological clues worthy of further analytical investigation.

The heterogeneity of early Parkinson's disease: a cluster analysis on newly diagnosed untreated patients.

Background The variability in the clinical phenotype of Parkinson’s disease seems to suggest the existence of several subtypes of the disease. To test this hypothesis we performed a cluster analysis using data assessing both motor and non-motor symptoms in a large cohort of newly diagnosed untreated PD patients. Methods We collected data on demographic, motor, and the whole complex of non-motor symptoms from 100 consecutive newly diagnosed untreated outpatients. Statistical cluster analysis allowed the identification of different subgroups, which have been subsequently explored. Results The data driven approach identified four distinct groups of patients, we have labeled: 1) Benign Pure Motor; 2) Benign mixed Motor-Non-Motor; 3) Non-Motor Dominant; and 4) Motor Dominant. Conclusion Our results confirmed the existence of different subgroups of early PD patients. Cluster analysis revealed the presence of distinct subtypes of patients profiled according to the relevance of both motor and non-motor symptoms. Identification of such subtypes may have important implications for generating pathogenetic hypotheses and therapeutic strategies.

Functional involvement of central cholinergic circuits and visual hallucinations in Parkinson's disease

Visual hallucinations (VHs) represent a frequent and disturbing complication of Parkinsons disease. Evidence suggests that VH can be related to central cholinergic dysfunction. Short-latency afferent inhibition (SAI) technique gives the opportunity to test an inhibitory cholinergic circuit in the human cerebral motor cortex. This inhibition of motor-evoked potentials can be observed when transcranial magnetic stimulation is delivered with a delay ranging from 2 to 8 ms, after a peripheral nerve afferent input has reached the somatosensory cortex. We applied SAI technique in 10 non-demented patients with Parkinsons disease with VHs, in 12 non-demented patients with Parkinsons disease without VHs (NVH-pts) and in 11 age-matched normal controls. All patients with Parkinsons disease underwent a battery of neuropsychological tests to assess frontal and visuospatial functions, memory and attention. SAI was significantly reduced in patients with VHs compared with controls and patients without VHs. Neuropsychological examination showed a mild cognitive impairment in 16 out of 22 patients with Parkinsons disease. In addition, we found that in our patients with VHs, performance of some tasks evaluating visuospatial functions and attentional/frontal lobe functions was significantly more impaired than in patients without VHs. SAI abnormalities, presence of VH and neuropsychological results strongly support the hypothesis of cholinergic dysfunction in some patients with Parkinsons disease, who will probably develop a dementia. A follow-up study of our patients is required to verify whether SAI abnormalities can predict a future severe cognitive decline. Moreover, SAI can also be very useful to follow-up the efficacy of anti-cholinesterase therapies.