Brain dysfunction in gait disorders of Caribbean atypical Parkinsonism and progressive supranuclear palsy patients: A comparative study

INTRODUCTION

Gait disorders and falls occur early in progressive supranuclear palsy (PSP-RS) and Caribbean atypical parkinsonism (Caribbean AP). However, the link between these signs and brain lesions has never been explored in these patient populations. Here, we investigate and compare the imaging factors that relate to gait and balance disorders in Caribbean AP and PSP-RS patients.

METHODS

We assessed gait and balance using clinical scales and gait recordings in 16 Caribbean AP and 15 PSP-RS patients and 17 age-matched controls. We measured the grey and white matter brain volumes on 3 T brain MRI images. We performed a principal component analysis (PCA) including all the data to determine differences and similarities between groups, and explore the relationship between gait disorders and brain volumes.

RESULTS

Both Caribbean AP patients and PSP-RS have marked gait and balance disorders with similar severity. In both groups, gait and balance disorders were found to be most strongly related to structural changes in the lateral cerebellum, caudate nucleus, and fronto-parietal areas. In Caribbean AP patients, gait disorders were also related to additional changes in the cortex, including frontal, insular, temporal and cuneus lobes, whereas in PSP-RS patients, additional white matter changes involved the mesencephalon and parahippocampal gyrus.

CONCLUSION

Gait and balance disorders in Caribbean AP patients are mainly related to dysfunction of cortical brain areas involved in visuo-sensorimotor processing and self-awareness, whereas these signs mainly result from premotor-brainstem-cerebellar network dysfunction in PSP-RS patients, brain areas involved in initiation and maintenance of locomotor pattern and postural adaptation.

A clinical and neurophysiological motor signature of Unverricht-Lundborg disease

OBJECTIVES

Unverricht-Lundborg disease (ULD) is the most common form of progressive myoclonus epilepsy. Cerebellar dysfunction may appear over time, contributing along with myoclonus to motor disability. The purpose of the present work was to clarify the motor and neurophysiological characteristics of ULD patients.

METHODS

Nine patients with genetically proven ULD were evaluated clinically (medical history collected from patient charts, the Scale for the Assessment and Rating of Ataxia and Unified Myoclonus Rating Scale). Neurophysiological investigations included EEG, surface polymyography, long-loop C-reflexes, somatosensory evoked potentials, EEG jerk-locked back-averaging (JLBA) and oculomotor recordings. All patients underwent brain MRI. Non-parametric Mann-Whitney tests were used to compare ULD patients' oculomotor parameters with those of a matched group of healthy volunteers (HV).

RESULTS

Myoclonus was activated by action but was virtually absent at rest and poorly induced by stimuli. Positive myoclonus was multifocal, often rhythmic and of brief duration, with top-down pyramidal temporospatial propagation. Cortical neurophysiology revealed a transient wave preceding myoclonus on EEG JLBA (n=8), enlarged somatosensory evoked potentials (n=7) and positive long-loop C-reflexes at rest (n=5). Compared with HV, ULD patients demonstrated decreased saccadic gain, increased gain dispersion and a higher frequency of hypermetric saccades associated with decreased peak velocity.

CONCLUSION

A homogeneous motor pattern was delineated that may represent a ULD clinical and neurophysiological signature. Clinical and neurophysiological findings confirmed the pure cortical origin of the permanent myoclonus. Also, oculomotor findings shed new light on ULD pathophysiology by evidencing combined midbrain and cerebellar dysfunction.

Lateral Temporal Lobe: An Early Imaging Marker of the Presymptomatic GRN Disease?

The preclinical stage of frontotemporal lobar degeneration (FTLD) is not well characterized. We conducted a brain metabolism (FDG-PET) and structural (cortical thickness) study to detect early changes in asymptomatic GRN mutation carriers (aGRN+) that were evaluated longitudinally over a 20-month period. At baseline, a left lateral temporal lobe hypometabolism was present in aGRN+ without any structural changes. Importantly, this is the first longitudinal study and, across time, the metabolism more rapidly decreased in aGRN+ in lateral temporal and frontal regions. The main structural change observed in the longitudinal study was a reduction of cortical thickness in the left lateral temporal lobe in carriers. A limit of this study is the relatively small sample (n = 16); nevertheless, it provides important results. First, it evidences that the pathological processes develop a long time before clinical onset, and that early neuroimaging changes might be detected approximately 20 years before the clinical onset of disease. Second, it suggests that metabolic changes are detectable before structural modifications and cognitive deficits. Third, both the baseline and longitudinal studies provide converging results implicating lateral temporal lobe as early involved in GRN disease. Finally, our study demonstrates that structural and metabolic changes could represent possible biomarkers to monitor the progression of disease in the presymptomatic stage toward clinical onset.

C9ORF72 repeat expansions in the frontotemporal dementias spectrum of diseases: a flow-chart for genetic testing

Frontotemporal dementia (FTD) refers to a disease spectrum including the behavioral variant FTD (bvFTD), primary progressive aphasia (PPA), progressive supranuclear palsy/corticobasal degeneration syndrome (PSP/CBDS), and FTD with amyotrophic lateral sclerosis (FTD-ALS). A GGGGCC expansion in C9ORF72 is a major cause of FTD and ALS. C9ORF72 was analyzed in 833 bvFTD, FTD-ALS, PPA, and PSP/CBDS probands; 202 patients from 151 families carried an expansion. C9ORF72 expansions were much more frequent in the large subgroup of patients with familial FTD-ALS (65.9%) than in those with pure FTD (12.8%); they were even more frequent than in familial pure ALS, according to estimated frequencies in the literature (23-50%). The frequency of carriers in non-familial FTD-ALS (12.7%) indicates that C9ORF72 should be analyzed even when family history is negative. Mutations were detected in 6.8% of PPA patients, and in 3.2% of patients with a clinical phenotype of PSP, thus enlarging the phenotype spectrum of C9ORF72. Onset was later in C9ORF72 (57.4 years, 95%CI: 55.9-56.1) than in MAPT patients (46.8, 95%CI: 43.0-50.6; p = 0.00001) and the same as in PGRN patients (59.6 years; 95%CI: 57.6-61.7; p = 0.4). ALS was more frequent in C9ORF72 than in MAPT and PGRN patients; onset before age 50 and parkinsonism were indicative of MAPT mutations, whereas hallucinations were indicative of PGRN mutations; prioritization of genetic testing is thus possible. Penetrance was age- and gender-dependent: by age 50, 78% of male carriers were symptomatic, but only 52% of females. This can also guide genetic testing and counseling. A flowchart for genetic testing is thus proposed.

Involvement of the supplementary eye field in oculomotor predictive behavior

The presentation of saccadic and smooth pursuit eye movements as two separate systems has recently been reconsidered: The two subsystems share a number of anatomical structures, and recent data suggest that this sharing also extends to physiological processes. The aim of our study was first to test whether these two subsystems share a common predictive process. We designed a new predictive smooth pursuit paradigm that requires the triggering of unpredictable saccades, performed either during low (ongoing pursuit) or high (pursuit direction reversal) predictive behavior. Saccade latency was used as a probe to reveal a possible sharing of prediction between the two subsystems. The main finding was that saccade latencies were markedly decreased when triggered around pursuit direction reversal and performed in the direction of the predicted pursuit. The aim of the second part of this study was to determine the neural substrate of this common predictive process. According to previous studies, the supplementary eye field (SEF) would be involved in the control of predictive pursuit. The same subjects therefore performed the same tasks, and transcranial magnetic stimulation (TMS) was applied over this area: Decreased saccade latencies were no longer observed, whereas it continued to be observed when applied over the occipital cortex. These results are consistent with (1) The existence of a common predictive process shared by both oculomotor subsystems; (2) The view of the SEF not as a primary oculomotor area but as a higher order structure able to elaborate complex processes, such as prediction, independently of the oculomotor output.

Inhibitory control of the human dorsolateral prefrontal cortex during the anti-saccade paradigm--a transcranial magnetic stimulation study

In the anti-saccade paradigm, subjects are instructed not to make a reflexive saccade to an appearing lateral target but to make an intentional saccade to the opposite side instead. The inhibition of reflexive saccade triggering is under the control of the dorsolateral prefrontal cortex (DLPFC). The critical time interval at which this inhibition takes place during the paradigm, however, is not exactly known. In the present study, we used single-pulse transcranial magnetic stimulation (TMS) to interfere with DLPFC function in 15 healthy subjects. TMS was applied over the right DLPFC either 100 ms before the onset of the visual target (i.e. -100 ms), at target onset (i.e. 0 ms) or 100 ms after target onset (i.e. +100 ms). Stimulation 100 ms before target onset significantly increased the percentage of anti-saccade errors to both sides, while stimulation at, or after, target onset had no significant effect. All three stimulation conditions had no significant influence on saccade latency of correct or erroneous anti-saccades. These findings show that the critical time interval at which the DLPFC controls the suppression of a reflexive saccade in the anti-saccade paradigm is before target onset. In addition, the results suggest the view that the triggering of correct anti-saccades is not under direct control of the DLPFC.

Visual vector inversion in the posterior parietal cortex

In the antisaccade task, a saccade must be triggered towards the mirror location of a visual target. The neural basis required for this visual vector inversion remains unclear, although neuronal activities reflecting this process have been recorded in the monkey lateral intraparietal area. We examined a patient with a small, right-sided, posterior parietal stroke who complained of difficulty in manipulating visual information. Antisaccades were markedly hypometric rightwards but normal leftwards. Largely unaffected performances in other saccade tasks revealed that visual and motor processing were not significantly affected. Antisaccade inaccuracy could therefore be ascribed to the impairment of visual vector inversion, a processing specifically required in this task. These findings provide the first evidence in humans that visual vector inversion could be an intrinsic property of the posterior parietal cortex.

Neurological, cardiological, and oculomotor progression in 104 patients with Friedreich ataxia during long-term follow-up

BACKGROUND

Friedreich ataxia (FA) is the most frequent autosomal recessive cerebellar ataxia. Although the phenotype is well known, disease progression has not been evaluated in a prospective manner.

OBJECTIVE

To perform a long-term prospective follow-up of neurological, cardiological, and oculomotor function in patients with FA (FA patients).

DESIGN

In this open-labeled prospective survey, we examined 104 FA patients every 6 months during a median period of 5 years (range, 6 months to 7 years), with a systematic standardized protocol. Data are reported as mean +/- SD.

SETTING

Neurological examinations were performed at the Federation of Neurology and the Department of Genetics of the Salpêtrière Hospital, Paris, France. Cardiological follow-up was performed at the Department of Cardiology; oculomotor examinations were performed at the Institut National de la Santé et de la Récherche Médicale Unit 679, at the same hospital. Patients We studied 104 FA patients with a confirmed molecular diagnosis. None were receiving antioxidant therapy at baseline; 88 accepted treatment with the coenzyme Q(10) analogue idebenone (5 mg/kg per day). Sixteen preferred not to be treated.

INTERVENTIONS

Neurological status was evaluated with the International Cooperative Ataxia Rating Scale (ICARS) and a quantitative writing test. Cardiological evaluations included echocardiography, electrocardiography, and Holter monitoring. Oculomotor function was evaluated by electro-oculography to determine the frequency of square wave jerks.

RESULTS

The total ICARS score worsened during follow-up, whether or not the patients were treated with idebenone (1.93 +/- 0.25 and 4.43 +/- 1.56 points per year, respectively). The total ICARS score increased faster in patients with onset before age 15 years compared with the others (2.6 +/- 0.4 [n = 51] vs 1.1 +/- 0.3 [n = 37]; P = .05). The posture subscore increased faster in patients able to stand at baseline, who also had shorter disease durations than patients unable to stand (1.25 +/- 0.12 vs 0.47 +/- 0.22 point per year; P<.001). Neurological progression was underestimated, however, by the ICARS scores, which reached a plateau in patients with long disease durations. Oculomotor function slightly deteriorated (0.09 +/- 0.02 Hz per year; P<.001). Left ventricular mass index decreased (-4.1 +/- 1.5 g/m(2) per year; P = .008), as did ejection fraction (-1.32% +/- 0.29% per year; P<.001).

CONCLUSIONS

The neurological condition of FA patients deteriorated slowly over time, even with idebenone treatment. Although cardiac hypertrophy decreased under treatment, cardiac function did not improve. The ICARS scale is not appropriate to evaluate the progression of FA in patients with long disease durations. Additional quantitative measures may improve the reliability of this scale.

Parkinson's disease with camptocormia

BACKGROUND

Camptocormia is defined as an abnormal flexion of the trunk that appears when standing or walking and disappears in the supine position. The origin of the disorder is unknown, but it is usually attributed either to a primary or a secondary paravertebral muscle myopathy or a motor neurone disorder. Camptocormia is also observed in a minority of patients with parkinsonism.

OBJECTIVE

To characterise the clinical and electrophysiological features of camptocormia and parkinsonian symptoms in patients with Parkinson's disease and camptocormia compared with patients with Parkinson's disease without camptocormia.

METHODS

Patients with parkinsonism and camptocormia (excluding patients with multiple system atrophy) prospectively underwent a multidisciplinary clinical (neurological, neuropsychological, psychological, rheumatological) and neurophysiological (electromyogram, ocular movement recording) examination and were compared with age-matched patients with Parkinson's disease without camptocormia.

RESULTS

The camptocormia developed after 8.5 (SD 5.3) years of parkinsonism, responded poorly to levodopa treatment (20%) and displayed features consistent with axial dystonia. Patients with camptocormia were characterised by prominent levodopa-unresponsive axial symptoms (ie, axial rigidity, gait disorder and postural instability), along with a tendency for greater error in the antisaccade paradigm.

CONCLUSION

We suggest that (1) the salient features of parkinsonism observed in patients with camptocormia are likely to represent a specific form of Parkinson's disease and camptocormia is an axial dystonia and (2) both camptocormia and parkinsonism in these patients might result from additional, non-dopaminergic neuronal dysfunction in the basal ganglia.

Decisional role of the dorsolateral prefrontal cortex in ocular motor behaviour

Three patients with a unilateral cortical lesion affecting the dorsolateral prefrontal cortex (DLPFC), i.e. Brodmann area 46, were tested using different paradigms of reflexive saccades (gap and overlap tasks), intentional saccades (antisaccades, memory-guided and predictive saccades) and smooth pursuit movements. Visually guided saccades with gap and overlap, latency of correct antisaccades and memory-guided saccades and the gain of smooth pursuit were normal, compared with controls. These results confirm our anatomical data showing that the adjacent frontal eye field (FEF) was unimpaired in these patients. The specific pattern of abnormalities after a unilateral DLPFC lesion, compared with that of the FEF lesions previously reported, consists mainly of: (i) a bilateral increase in the percentage of errors in the antisaccade task (misdirected reflexive saccades); (ii) a bilateral increase in the variable error in amplitude, without significant decrease in the gain, in the memory-guided saccade task; and (iii) a bilateral decrease in the percentage of anticipatory saccades in the predictive task. Taken together, these results suggest that the DLPFC plays a crucial role in the decisional processes, preparing saccades by inhibiting unwanted reflexive saccades (inhibition), maintaining memorized information for ongoing intentional saccades (short-term spatial memory) or facilitating anticipatory saccades (prediction), depending upon current external environmental and internal circumstances.

Cortical control of spatial memory in humans: the visuooculomotor model

We review current knowledge of the cortical control of spatial memory, studied using visuooculomotor paradigms. Spatial memory is an essential cognitive process that can be involved in preparing motor responses. Our knowledge of spatial memory in humans recently has progressed thanks to the use of ocular saccades as a convenient model of motor behavior. Accuracy of memory-guided saccades, made to the remembered locations of visual targets, is a reflection of spatial memory. For the performance of memory-guided saccades with brief delays (up to 15-20 seconds), that is, involving short-term spatial memory, lesion studies have shown that the posterior parietal cortex, the dorsolateral prefrontal cortex, and the frontal eye field play significant roles. Studies of memory-guided saccades using transcranial magnetic stimulation have suggested that the right posterior parietal cortex is involved at the initial stage (<300 milliseconds) of visuospatial integration, whereas the dorsolateral prefrontal cortex in both hemispheres controls the following phase of short-term memorization, the frontal eye field mainly serving to trigger saccades. The new concept of a medium-term spatial memory has emerged from a behavioral study of memory-guided saccades in normal subjects, showing a paradoxical spontaneous improvement of spatial memory after delays of approximately 20 seconds. Lesion studies have shown that the parahippocampal cortex could specifically control this medium-term spatial memory. Last, different experimental and clinical arguments suggest that, after a few minutes, the hippocampal formation finally takes over the control of spatial memory for long-term spatial memorization. Therefore, spatial memory involved in the memorization of visual items could be successively controlled by the dorsolateral prefrontal cortex (short-term spatial memory), the parahippocampal cortex (medium-term spatial memory), and the hippocampal formation (long-term spatial memory), depending on specific periods of times. The applicability of this simple visuooculomotor model of spatial memory to other types of stimuli and general motoricity has yet to be confirmed.

Effects of cortical lesions on saccadic: eye movements in humans

Our knowledge of the cortical control of saccadic eye movements (saccades) in humans has recently progressed mainly because of lesion and transcranial magnetic stimulation (TMS) studies, but also because of functional imaging. It is now well known that the frontal eye field is involved in the control of intentional saccades, the parietal eye field in that of reflexive saccades, the supplementary eye field (SEF) in the initiation of motor programs comprising saccades, the pre-SEF in the learning of these programs, and the dorsolateral prefrontal cortex (DLPFC) in saccade inhibition, prediction and spatial working memory. Saccades may also be used as a convenient model of motricity to study general cognitive processes such as motivation and spatial memory. Thus, it has been shown that the posterior part of the anterior cingulate cortex, called the cingulate eye field, is involved in motivation and the preparation of all intentional saccades, but not in reflexive saccades. Recently, our understanding of the cortical control of spatial memory has noticeably progressed by using the simple visuo-oculomotor model represented by the memory-guide saccade paradigm, in which a single saccade is made to the remembered position of a unique visual item presented a while before. Transcranial magnetic stimulation studies have determined that after a brief stage of spatial integration in the posterior parietal cortex (inferior to 300 ms), short-term spatial memory (i.e., up to 15-20 seconds) is controlled by the DLPFC. Behavioral and lesion studies have shown that medium-term spatial memory (between 15 and 20 seconds and a few minutes) is specifically controlled by the parahippocampal cortex, before long-term memorization (i.e., after a few minutes) in the hippocampal formation. These different but complementary study methods used in humans have thus contributed to a better understanding of both eye movement physiology and general cognitive processes preparing motricity as whole.

Memory guided saccade deficit after caudate nucleus lesion

The role of the caudate nucleus in ocular motor control is not well determined in humans. Eye movements were recorded from a 45 year old man with infarctions involving bilaterally the body of the caudate nucleus, with a greater extent on the left side. The patient exhibited a pattern of eye movement abnormalities in which a delay dependent decrease of accuracy of memory guided saccades predominated. By contrast, memory guided pointing was normal. It is concluded that the body of the caudate nucleus participates in a spatial short term memory network devoted to eye movements.

Spatial memory deficits in patients with lesions affecting the medial temporal neocortex

Lesion studies in monkeys suggest that neocortical subregions of the medial temporal lobe (MTL) carry memory functions independent of the hippocampal formation. The present study investigates possible differential contributions of MTL subregions to spatial memory in humans. Eye movements toward remembered spatial cues (memory-guided saccades) with unpredictably varied memorization delays of up to 30 seconds were recorded in patients with postsurgical lesions of the right MTL, either restricted to the hippocampal formation (n = 3) or including the adjacent neocortex (n = 5) and in 10 controls. Although saccadic targeting errors of patients with selective hippocampal lesions did not differ from controls, saccadic targeting errors of patients with additional neocortical involvement showed a significant and contralaterally pronounced increase at memorization delays above 20 seconds. We conclude that the human medial temporal neocortex carries spatial memory functions independent of the hippocampal formation and distinct from spatial short-term memory.

Eye movement abnormalities correlate with genotype in autosomal dominant cerebellar ataxia type I

We compared horizontal eye movements (visually guided saccades, antisaccades, and smooth pursuit) in control subjects (n = 14) and patients with three forms of autosomal dominant cerebellar ataxias type I: spinocerebellar ataxias 1 and 2 (SCA1, n = 11; SCA2, n = 10) and SCA3/Machado-Joseph disease (MJD) (n = 16). In SCA1, saccade amplitude was significantly increased, resulting in hypermetria. The smooth pursuit gain was decreased. In SCA2, saccade velocity was markedly decreased. The percentage of errors in antisaccades was greatly increased and was significantly correlated with age at disease onset. In addition, a correlation between smooth pursuit gain and the number of trinucleotide repeats was found. In SCA3, gaze-evoked nystagmus was often present as was saccade hypometria and smooth pursuit gain was markedly decreased. Three major criteria, saccade amplitude, saccade velocity, and presence of gaze-evoked nystagmus, permitted the correct assignment of 90% of the SCA1, 90% of the SCA2, and 93% of the patients with SCA3 to their genetically confirmed patient group and, therefore, may help orient diagnoses of SCA1, SCA2, and SCA3 at early clinical stages of the diseases.