Structural Connectivity and Cortical Thickness Alterations in Transient Global Amnesia.

BACKGROUND AND PURPOSE: Transient global amnesia (TGA) is a sudden onset of anterograde and retrograde amnesia. We aimed to assess differences in terms of cortical thickness and structural brain connectome between patients with TGA (at acute and delayed postrecovery stages) and matched controls. MATERIALS AND METHODS: We report on 18 consecutive patients with TGA who underwent 3T MR imaging, including DTI and MPRAGE sequences, at the acute (mean delay postonset: 44 hours) and delayed post-recovery (mean delay: 35 days) stages. Structural connectome was assessed in patients with TGA and in 18 age- and sex-matched controls by using probabilistic fiber- tracking and segmentation of 164 cortical/subcortical structures ("nodes"). Connectivity graphs were computed and global network metrics were calculated. Network-based statistical analysis (NBS) was applied to compare patients with TGA at each stage with controls. We also compared cortical thickness between patients with TGA and healthy controls. RESULTS: Global network metrics were not altered in patients with TGA. NBS-analysis showed structural connectome alterations in patients with TGA compared with controls, in core regions involving the limbic network, with 113 nodes and 114 connections (33 left intrahemispheric, 31 right intrahemispheric, and 50 interhemispheric connections) showing significantly decreased structural connectivity (P < .05 NBS corrected, t-values ranging from 3.03 to 8.73). Lower cortical thickness compared with controls was associated with these structural alterations in patients with TGA, involving the orbitofrontal, cingulate, and inferior temporal cortices. All the abnormalities were visible at both acute and delayed postrecovery stages. CONCLUSIONS: Our preliminary study suggests there are structural abnormalities of the limbic network in patients with TGA compared with controls, including decreased structural connectivity and cortical thickness.

[Usefulness of molecular genetic analysis of the PRNP gene in patients with cerebellar ataxia: a new case of fatal familial insomnia]. / Intérêt de l'étude génétique du gène PRNP devant un syndrome cérébelleux: à propos d'un nouveau cas d'insomnie fatale familiale.

We report the fifth French case of fatal familial insomnia, characterized by a mutation at codon 178 of prion protein gene and by heterozygoty (Met/Val) at codon 129. The clinical picture included cerebellar ataxia, dysautonomia and frontal lobe syndrome. Prion protein gene analysis was performed in order to support a diagnosis of Creutzfeldt-Jakob disease and assert the diagnosis of fatal familial insomnia. Neuropathologic analysis showed unusual changes including severe neuronal loss in the inferior olive and the dentate nucleus, and absence of obvious lesions in the thalamus. Moreover, spongiform changes were moderate in the superior temporal cortex and the occipital cortex. There was no spongiform change in frontal cortex. Abnormal prion protein (PrP(res)) was mainly evidenced in the parietal cortex. Molecular genetic study of the PRNP gene should be performed in patients who present with a cerebellar ataxia of equivocal origin.

[Vasculitis confined to the peripheral nervous system: atypical clinical presentation]. / Vascularite restreinte au système nerveux périphérique: présentation clinique atypique.

INTRODUCTION: Peripheral neuropathy is a common feature of many vasculitic syndromes. In some patients, the neuropathy may be the sole manifestation of vasculitis. EXEGESIS: A 74-year-old lady complained of pain and weakness of the lower limbs. In her history, we noted right optic neuritis, monoclonal gammopathy and dyslipidemia treated by fenofibrate. Clinical examination showed proximal muscle strength deficit of lower limbs, with quadriceps femoral muscles atrophy. Muscle stretch reflexes were absent. There was no deficit in light touch and pain sensation, but proprioception was impaired. There was electromyographic evidence of myopathic impairment with abnormal spontaneous activity. Amplitude of the sensory action potentials was mildly reduced. Laboratory tests were normal. Fenofibrate was stopped, but the clinical symptoms increased. Four months later, another electrophysiological study showed a very reduced amplitude of sensory action potentials. Myopathic impairment was less severe. Nerve biopsy showed inflammation and necrosis of nerve arteries, which lead to the diagnosis of necrotizing vasculitis. A corticosteroid treatment was done. Six months later, clinical and electrophysiological improvement clearly appeared. CONCLUSION: Histological lesions of vasculitis confined to the peripheral nervous system are those of classic polyarteritis nodosas. There is no systemic involvement nor biological abnormalities, which strengthens the role of nerve and muscle biopsy. The prognosis is good after corticosteroid treatment, which is not the case with systemic vasculitis.

[Refsum's disease: evolution 35 years after diagnosis]. / Maladie de Refsum avec 35 ans de recul.

Refsum's disease (Heredopathia atactica polyneuritiformis) is an autosomal recessive disease caused by a defective alpha oxidation of a C20 fatty acid: the phytanic acid. Deficiency of a peroxysomal enzyme called "Phytanoyl-Co-A alpha hydroxylase" leads to an accumulation of phytanic acid. The clinical picture include retinitis pigmentosa, peripheral neuropathy, ataxia and elevated cerebrospinal fluid protein concentration. Firstly described in 1946 by Sigvald Refsum, dietary treatment leads to an improvement of neurological symptoms but does not affect retinal changes. To our knowledge, there is no data in the literature on long term follow-up. A patient with Refsum's disease diagnosed in 1965 presented with facial paralysis. The phytanic acid concentration was low, CSF protein level was normal leading to diagnosis of Bell's palsy. This observation is of particular interest because after 35 years evolution of the disease, the only handicap was visual impairment, with no loss of muscle strength or sensory deficit.

[Pernicious anemia]. / Syndrome neuro-anémique.

Pernicious anaemia is the most common cause of cobalamin deficiency. Nervous disorders associated with cobalamin deficiency are neuropathy, optic atrophy, dementia and myelopathy (subacute combined degeneration). In this case, symptoms are those of posterior and lateral column dysfunction of the spinal cord, with diminished vibratory sensation, ataxia, weakness of limbs, hyperreflexia, extensor plantar response and spasticity. Macrocytosis and anaemia are often lacking. There is an inverse correlation between the degree of anaemia and the extent of nervous impairment. The most sensitive tool for the diagnosis of cobalamin deficiency is the serum cobalamin level. But a normal cobalamin assay does not fully exclude cobalamin deficiency. Levels of serum methylmalonic acid and total homocysteine are useful as ancillary tests in the diagnosis. Treatment is based on intramuscular injections of vitamin B12.

[Electrophysiological diagnosis of neurogenic thoracic outlet syndrome]. / Diagnostic électrophysiologique du syndrome neurologique de la traversée thoraco-brachiale.

The neurogenic thoracic outlet syndrome includes the symptoms caused by the compression of the brachial plexus at some point between the interscalene triangle and the inferior border of the axilla. Five patients diagnosed as having neurogenic thoracic outlet syndrome were examined. We determinated clinical and electrophysiological features which lead to thoracic outlet syndrome diagnosis. The clinical features included paresthesia and pain along the inner part of the arm, forearm and hand. Diminished sensation was rare. Muscle weakness was usual and muscle atrophy was associated in severe cases. The association with a lower cervical rib was useful. Electrodiagnostic studies always showed abnormalities. Electromyographic studies showed a reduced recruitment pattern of motor unit activation in intrinsic hand muscles. The medial antebrachial cutaneous nerve action potential amplitude was low. Nerve conduction studies also showed loss of amplitude of the ulnar sensory and median motor responses.