The role of dentate nuclei in human oculomotor control: insights from cerebrotendinous xanthomatosis.

KEY POINTS: A cerebellar dentate nuclei (DN) contribution to volitional oculomotor control has recently been hypothesized but not fully understood. Cerebrotendinous xanthomatosis (CTX) is a rare neurometabolic disease typically characterized by DN damage. In this study, we compared the ocular movement characteristics of two sets of CTX patients, with and without brain MRI evidence of DN involvement, with a set of healthy subjects. Our results suggest that DN participate in voluntary behaviour, such as the execution of antisaccades, and moreover are involved in controlling the precision of the ocular movement. The saccadic abnormalities related to DN involvement were independent of global and regional brain atrophy. Our study confirms the relevant role of DN in voluntary aspects of oculomotion and delineates specific saccadic abnormalities that could be used to detect the involvement of DN in other cerebellar disorders. ABSTRACT: It is well known that the medial cerebellum controls saccadic speed and accuracy. In contrast, the role of the lateral cerebellum (cerebellar hemispheres and dentate nuclei, DN) is less well understood. Cerebrotendinous xanthomatosis (CTX) is a lipid storage disorder due to mutations in CYP27A1, typically characterized by DN damage. CTX thus provides a unique opportunity to study DN in human oculomotor control. We analysed horizontal and vertical visually guided saccades and horizontal antisaccades of 19 CTX patients. Results were related to the presence/absence of DN involvement and compared with those of healthy subjects. To evaluate the contribution of other areas, abnormal saccadic parameters were compared with global and regional brain volumes. CTX patients executed normally accurate saccades with normal main sequence relationships, indicating that the brainstem and medial cerebellar structures were functionally spared. Patients with CTX executed more frequent multistep saccades and directional errors during the antisaccade task than controls. CTX patients with DN damage showed less precise saccades with longer latencies, and more frequent directional errors, usually not followed by corrections, than either controls or patients without DN involvement. These saccadic abnormalities related to DN involvement but were independent of global and regional brain atrophy. We hypothesize that two different cerebellar networks contribute to the metrics of a movement: the medial cerebellar structures determine accuracy, whereas the lateral cerebellar structures control precision. The lateral cerebellum (hemispheres and DN) also participates in modulating goal directed gaze behaviour, by prioritizing volitional over reflexive movements.

Allogeneic haematopoietic stem cell transplantation for mitochondrial neurogastrointestinal encephalomyopathy.

Haematopoietic stem cell transplantation has been proposed as treatment for mitochondrial neurogastrointestinal encephalomyopathy, a rare fatal autosomal recessive disease due to TYMP mutations that result in thymidine phosphorylase deficiency. We conducted a retrospective analysis of all known patients suffering from mitochondrial neurogastrointestinal encephalomyopathy who underwent allogeneic haematopoietic stem cell transplantation between 2005 and 2011. Twenty-four patients, 11 males and 13 females, median age 25 years (range 10-41 years) treated with haematopoietic stem cell transplantation from related (n = 9) or unrelated donors (n = 15) in 15 institutions worldwide were analysed for outcome and its associated factors. Overall, 9 of 24 patients (37.5%) were alive at last follow-up with a median follow-up of these surviving patients of 1430 days. Deaths were attributed to transplant in nine (including two after a second transplant due to graft failure), and to mitochondrial neurogastrointestinal encephalomyopathy in six patients. Thymidine phosphorylase activity rose from undetectable to normal levels (median 697 nmol/h/mg protein, range 262-1285) in all survivors. Seven patients (29%) who were engrafted and living more than 2 years after transplantation, showed improvement of body mass index, gastrointestinal manifestations, and peripheral neuropathy. Univariate statistical analysis demonstrated that survival was associated with two defined pre-transplant characteristics: human leukocyte antigen match (10/10 versus <10/10) and disease characteristics (liver disease, history of gastrointestinal pseudo-obstruction or both). Allogeneic haematopoietic stem cell transplantation can restore thymidine phosphorylase enzyme function in patients with mitochondrial neurogastrointestinal encephalomyopathy and improve clinical manifestations of mitochondrial neurogastrointestinal encephalomyopathy in the long term. Allogeneic haematopoietic stem cell transplantation should be considered for selected patients with an optimal donor.

Hand muscles corticomotor excitability in hereditary spastic paraparesis type 4.

Transcranial magnetic stimulation (TMS) studies on the pathways to the upper limbs have revealed inconsistent results in patients harboring mutations in SPAST/SPG4 gene, responsible for the commonest form of hereditary spastic paraplegia (HSP). This paper is addressed to study the corticomotor excitability of the pathways to the upper limbs in SPG4 subjects. We assessed the corticomotor excitability of hand muscles in 12 subjects belonging to 7 unrelated SPG4 families and in 12 control subjects by stimulus-response curve [input-output (I-O) curve]. All the parameters of the recruitment curve (threshold, V50, slope and plateau) did not differ significantly from those of the controls. Presence of upper limb hyper-reflexia did not influence the results of I-O curve. Considering the multiplicity of possible genes/loci accounting for pure HSPs, performing TMS analyses could be helpful in differential diagnosis of pure HSPs in the absence of other clinical or neuroimaging tools.

Visual system involvement in CADASIL.

BACKGROUND AND OBJECTIVE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary arteriolar small-vessel disease caused by Notch3 mutations. A detailed definition of the neuro-ophthalmologic spectrum of CADASIL might provide new insights in the pathophysiology of small-vessel diseases. Therefore, this study aims to precisely delineate the features and the prevalence of the visual system impairment in CADASIL. METHODS: A cohort of 34 genetically confirmed CADASIL patients was enrolled in an observational cross-sectional study. Subjects underwent a complete neuro-ophthalmological evaluation. Clinical features and common cardiovascular risk factors were also considered. Data were compared with those already reported in previous studies. RESULTS: Both afferent and efferent visual structures were commonly impaired in CADASIL patients. Retinal microvascular changes such as arteriolar narrowing and arteriovenous nicking, described in most patients and detected also in asymptomatic carriers, reflect the typical hemodynamic changes of CADASIL. However, less frequent findings, like early macular and lens changes, would indicate a possible further role played by susceptibility to premature aging and degeneration. Cotton wool spots and vessel occlusions were not common. Finally, eye movement abnormalities suggest that the brainstem is particularly vulnerable to damage in CADASIL. CONCLUSIONS: Although no specific or prominent neuro-ophthalmologic finding can be considered as hallmark of the disease, afferent and efferent visual system abnormalities could be accounted as complementary markers to study cerebral small-vessel diseases.

Sonographic and electrodiagnostic features of hereditary neuropathy with liability to pressure palsies.

In hereditary neuropathy with liability to pressure palsies (HNPP), the increase in distal motor latencies (DMLs) is often out of proportion to the slowing of conduction velocities, but the pathophysiological mechanism is still unclear. We used a combined electrophysiological and ultrasonographic (US) approach to provide insight into this issue. Twelve HNPP subjects underwent extensive electrophysiological studies and US measurements of the cross-sectional area (CSA) of several peripheral nerves. US nerve enlargement was only observed in the carpal tunnel, Guyon's canal, the elbow and the fibular head. We did not observe US abnormalities at sites where nerve entrapment is uncommon. An increase in DMLs was observed regardless of US nerve enlargement. The increased nerve CSA only in common sites of entrapment likely reflected the well-documented nerve vulnerability to mechanical stress in HNPP. No morphometric changes were seen in the distal nerve segments where compression/entrapment is unlikely, despite the fact that the DMLs were increased. These data suggest that factors other than mechanical stress are responsible for the distal slowing of action potential propagation. We speculate that a mixture of mechanical insults and an axon-initiated process in the distal nerves underlies the distal slowing and/or conduction failure in HNPP.

Differences in saccade dynamics between spinocerebellar ataxia 2 and late-onset cerebellar ataxias.

The cerebellum is implicated in maintaining the saccadic subsystem efficient for vision by minimizing movement inaccuracy and by learning from endpoint errors. This ability is often disrupted in degenerative cerebellar diseases, as demonstrated by saccade kinetic abnormalities. The study of saccades in these patients may therefore provide insights into the neural substrate underlying saccadic motor control. We investigated the different extent of saccade dynamic abnormalities in spinocerebellar ataxia type 2 and late-onset cerebellar ataxias, genetically undefined and with prevalent cerebellar atrophy. Reflexive and voluntary saccades of different amplitude (10°-18°) were studied in seven patients with spinocerebellar ataxia 2, eight patients with late-onset cerebellar ataxia and 25 healthy controls. Quantitative analysis of saccade parameters and measures of saccade accuracy were performed. Detailed neurological, neurophysiological and magnetic resonance imaging assessment was obtained for each patient. Genetic and laboratory screening for spinocerebellar ataxias and other forms of late-onset cerebellar ataxias were also performed. A lower peak saccade velocity and longer duration was observed in patients with spinocerebellar ataxia 2 with respect to those with late-onset cerebellar ataxia and controls. Unlike subjects with spinocerebellar ataxia 2, patients with late-onset cerebellar ataxia showed main sequence relationships to similar saccades made by normal subjects. Saccades were significantly more inaccurate, namely hypometric, in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and inaccuracy increased with saccade amplitude. The percentage of hypometric primary saccades and of larger secondary corrective saccades were consistently higher in late-onset cerebellar ataxia than in spinocerebellar ataxia 2 and controls. No other significant differences were found between groups. Two different mechanisms were adopted to redirect the fovea as fast and/or accurately as possible to peripheral targets by the two groups of cerebellar patients. Patients with spinocerebellar ataxia 2 maintained accuracy using slow saccades with longer duration. This reflects prevalent degenerative processes affecting the pontine burst generator and leading to saccade velocity failure. On the other hand, patients with late-onset cerebellar ataxia reached the target with a number of fast inaccurate, mostly hypometric saccades. Different degrees of cerebellar oculomotor vermis involvement may account for differences in optimizing the trade-off between velocity and accuracy in the two groups. In addition, as suggested by spinocerebellar patients having slow saccades that are no longer ballistic, visual feedback might be continuously available during the movement execution to guide the eye to its target.

Bone marrow-derived progenitor cells in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy.

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited disease due to cerebral microangiopathy presenting with variable pictures, including stroke, progressive cognitive impairment, and disability. Mechanisms leading from vessel structural changes to parenchymal damage and eventually to clinical expression are not fully understood. Among pathogenic processes, endothelial dysfunction has been hypothesized. Endothelial progenitor cells and circulating progenitor cells (CPCs) derived from bone marrow participate in endothelium structure and function maintenance and contribute to ischemic area revascularization. No data are available about these cells in CADASIL. Our objective in this study was to evaluate endothelial progenitor cells and CPCs role in CADASIL. METHODS: Twenty-nine patients with CADASIL and 29 sex- and age-matched control subjects were enrolled. Cells were measured in peripheral blood using flow cytometry. Endothelial progenitor cells were defined as positive for CD34/KDR, CD133/KDR, and CD34/CD133/KDR; and CPCs as positive for CD34, CD133, and CD34/CD133. RESULTS: Endothelial progenitor cells were significantly lower in patients with CADASIL than in control subjects (CD34/KDR: 0.05 versus 0.1 cells/microL, P=0.005; CD133/KDR: 0.07 versus 0.1 cells/microL, P=0.006; CD34/CD133/KDR: 0.05 versus 0.1 cells/microL, P=0.001). The difference remained significant after adjusting for age, sex, and statin use. CPCs were not significantly lower in CADASIL, but patients with stroke or dementia had significantly reduced CPC levels than patients without (CD34: 1.68 versus 2.95 cells/microL, P=0.007; CD133: 1.40 versus 2.82 cells/microL, P=0.004; CD34/CD133: 1.44 versus 2.75 cells/microL, P=0.004). CPC levels significantly correlated with cognitive and motor performance measures. CONCLUSIONS: We have documented an association between endothelial progenitor cells and CPCs and CADASIL, extending previous data about the presence of endothelial dysfunction in this disease and its potential role in modulating phenotype.

Neurophthalmologic and Orthoptic Ambulatory Assessments Reveal Ocular and Visual Changes in Patients With Early Alzheimer and Parkinson's Disease.

Patients with Alzheimer's disease (AD) and Parkinson's disease (PD) develop a progressive decline of visual function. This condition aggravates overall cognitive and motor abilities, is a risk factor for developing hallucinations, and can have a significant influence on general quality of life. Visual problems are common complaints of patients with PD and AD in the early stages of the disease, but they also occur during normal aging, making it difficult to differentiate between normal and pathological conditions. In this respect, their real incidence has remained largely underestimated, and no rehabilitative approaches have been standardized. With the aim to increase awareness for ocular and visual disorders, we collected the main neurophthalmologic and orthoptic parameters, including optical coherence tomography (OCT), in six patients with a diagnosis of PD, six patients with a diagnosis of early AD, and eight control subjects in an easily assessable outpatient setting. We also evaluated the patient's ability to recognize changes in facial expression. Our study demonstrates that visual problems, including blurred vision, diplopia, reading discomfort, photophobia, and glare, are commonly reported in patients with PD and AD. Moreover, abnormal eye alignment and vergence insufficiency were documented in all patients during examination. Despite the small size of the sample, we demonstrated greater ganglion cell and retinal nerve fibers layer (RNFL) damage and a defect of facial emotion recognition in AD/PD patients with respect to a comparable group of normal elderly persons, with peculiarities depending upon the disease. Ocular defects or visual discomfort could be correctly evaluated in these patients and possibly corrected by means of lens, orthoptic exercises, and visual rehabilitation. Such a practical approach may help to ameliorate motor autonomy, reading ability, and may also reduce the risk of falls, with a positive impact in daily living activities.

Right-to-left shunt in CADASIL patients: prevalence and correlation with clinical and MRI findings.

BACKGROUND AND PURPOSE: A high prevalence of right-to-left shunt (RLS) was described in a family of patients with CADASIL, a rare cerebral arteriopathy attributable to Notch3 gene mutations. The aim of this study was to determine the prevalence of RLS in patients with CADASIL and possible relation to clinical phenotype and cerebral MRI lesion load. METHODS: Twenty-three CADASIL patients underwent Transcranial Doppler with gaseous contrast to asses RLS. Correlations between RLS, clinical features, and MRI lesion volume (LV) were determined. RESULTS: Large RLS was diagnosed in 47% of patients. No significant clinical or MRI differences were found between patients with and without RLS. CONCLUSIONS: We found a high prevalence of RLS in our group of CADASIL patients. This may not be a coincidence, but can be rather related to the role of the Notch receptor family in the development of cardiovascular system.

Cardiac autonomic nervous system and risk of arrhythmias in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited systemic microangiopathy with prevalently cerebral manifestations. Among the causes of death, sudden unexpected death seems to occur in a significant number of CADASIL patients. Because potential causes of sudden unexpected death may include cardiac arrhythmias and myocardial infarction, we evaluated risk factors for life-threatening arrhythmias, such as reduced heart rate variability, sympathetic overactivity and QT interval (QTc) prolongation, in 23 CADASIL patients. The relationship of these changes with brain MRI pattern was also investigated. METHODS: Frequency domain measures of heart rate variability (10 minutes recordings) and QTc interval were recorded in 23 CADASIL patients (17 males, 6 females) and 22 healthy age- and sex-matched control subjects. The following heart rate variability spectral parameters were considered at rest during spontaneous and controlled breathing (Cb): total power, very-low-frequency component, low-frequency component, high-frequency component, low-frequency/high-frequency ratio, and Cb-total power, Cb-very-low-frequency component, Cb-low-frequency component, Cb-high-frequency component, Cb-low-frequency/high-frequency ratio. R-to-R wave and QTc interval were also analyzed. All data were statistically compared between CADASIL and control subjects. Conventional brain MRI was performed in patients with CADASIL and T1-weighted and T2-weighted lesion volumes, and were compared with each spectral component of the tachogram. RESULTS: During spontaneous and controlled breathing, total power spectrum and all spectral components (very low frequency component, high-frequency component, low-frequency component) of heart rate variability were significantly reduced in CADASIL patients with respect to controls (P<0.05). The low-frequency/high-frequency component ratio was significantly higher in CADASIL patients than in controls. No significant correlation between heart rate variability spectral parameters and other variables including total brain T2-weighted and T1-weighted lesion volumes were observed in CADASIL subjects. CONCLUSIONS: We found a statistically significant reduction in all frequency domain parameters of heart rate variability associated with a higher low frequency/high frequency ratio for CADASIL patients with respect to normal subjects. These data are consistent with autonomic derangement and suggests that CADASIL patients may be at risk for life-threatening arrhythmias. This could at least in part explain their higher recurrence of sudden unexpected death and should be taken into account in planning therapy.

Cortical damage in brains of patients with adult-form of myotonic dystrophy type 1 and no or minimal MRI abnormalities.

OBJECTIVE: To evaluate, by using quantitative MRI metrics, subtle cortical changes in brains of patients with the adult form of myotonic dystrophy type I (DM1) who showed no or minimal abnormalities on MRI. BACKGROUND: DM1 is an autosomal dominant multisystem disorder caused by the expansion of CTG repeats in the myotonic dystrophy-protein kinase gene. Mild to severe involvement of the CNS can be part of the clinical features of the disease. Several MRI studies have demonstrated that both focal white matter (WM) lesions and diffuse grey matter atrophy can be found in the brains of DM1 patients. However, whether these two processes are related or may occur independently is not clear. DESIGN/METHODS: Ten genetically-proven DM1 patients who showed no or minimal abnormalities on MRI underwent a new brain MRI examination to obtain computerized measures of total and regional brain volumes normalized to head size and regional measurements of the magnetization transfer ratio (MTr). RESULTS: Normalized brain volumes (NBV) were significantly (p < 0.0001) lower in DM1 subjects than in a group of age- and sex-matched normal controls. Normalized cortical volumes (NCV) also were lower (p = 0.003) in DM1 subjects than in normal controls, whereas normalized WM volumes were not different between the two groups (p = 0.3). In agreement with this, values of MTr in the neocortex (cortical-MTr) were significantly (p = 0.006) lower in DM1 patients than in normal controls and this difference was not found in the WM tissue (p = 0.8). CONCLUSIONS: Neocortical damage seems to be evident in the absence of visible WM lesions suggesting that a neocortical pathology, unrelated to WM lesion formation, occurs in DM1 brains.

APOE ɛ2 is associated with white matter hyperintensity volume in CADASIL.

Apolipoprotein E (APOE) increases the risk for Alzheimer's disease (ɛ4 allele) and cerebral amyloid angiopathy (ɛ2 and ɛ4), but its role in small vessel disease (SVD) is debated. Here we studied the effects of APOE on white matter hyperintensity volume (WMHV) in CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy), a nonamyloidogenic angiopathy and inherited early-onset form of pure SVD. Four hundred and eighty-eight subjects were recruited through a multicenter consortium. Compared with APOE ɛ3/ɛ3, WMHV was increased in APOE ɛ2 (P = 0.02) but not APOE ɛ4. The results remained significant when controlled for genome-wide genetic background variation. Our findings suggest a modifying influence of APOE ɛ2 on WMHV caused by pure SVD.

MR evidence of structural and metabolic changes in brains of patients with Werner's syndrome.

OBJECTIVE: To assess CNS abnormalities in patients with Werner's syndrome (WS) using MR metrics specific for tissue damage. BACKGROUND: WS is a rare autosomal recessive disorder that causes premature aging. The CNS involvement in this disease is still debated. METHODS: Two siblings who showed signs of neurological involvement underwent MR spectroscopic imaging (MRSI) and magnetization transfer (MT) imaging. Also, on conventional T1-weighted MR images, measurements of total brain volume were performed. RESULTS: Conventional MR images of both WS patients did not show abnormalities on visual inspection. However, both WS patients showed significantly lower values of normalized total brain volume and MT ratio in the white matter than age-matched normal controls. Also, proton MRSI showed significantly lower values of central brain NAA/Cr in WS patients than in normal controls. CONCLUSIONS: Our findings suggest that, despite normal appearance on conventional MRI, diffuse structural and metabolic tissue damage can be demonstrated in WS brains by means of sensitive MR methods even in patients with moderate or subclinical CNS involvement.

Quantification of brain damage in cerebrotendinous xanthomatosis with magnetization transfer MR imaging.

BACKGROUND AND PURPOSE: Conventional MR imaging for quantification of brain damage in monitoring the evolution of cerebrotendinous xanthomatosis (CTX) has limitations. Magnetization transfer (MT) MR imaging is overcoming these limitations. Using MT MR imaging, we sought to quantify, in vivo, the extent of brain and cerebellar damage in patients with CTX, with the ulimate goal to investigate the magnitude of the correlation between MT MR imaging findings and clinical disability. METHODS: Conventional and MT MR images of the brain were obtained in nine patients with CTX and in 10 sex- and age-matched healthy volunteers. MT ratio histograms were derived of the whole brain, brain normal-appearing white matter (NAWM), brain normal-appearing gray matter (NAGM), cerebellar NAWM, and cerebellar NAGM. Clinical disability was measured by using the Expanded Disability Status Scale (EDSS). RESULTS: Average MT ratio and peak heights of the whole brain, brain NAWM, and brain NAGM histograms in patients with CTX were significantly lower than the corresponding quantities in the control subjects. All cerebellar NAGM MT ratio histogram-derived metrics and average MT ratio of the cerebellar NAWM histogram in patients with CTX were also significantly lower than the corresponding quantities in the control subjects. Strong correlations were found between the EDSS score and a composite whole-brain MT ratio histogram score (r = 0.77, P <.01) and a composite brain white matter MT ratio histogram score (r = 0.71, P <.03). A strong correlation was also found between the cerebellar functional system score and a composite cerebellar NAWM score (r = 0.72, P <.02). CONCLUSION: The quantitative assessment of brain damage in patients with CTX with use of MT MR imaging can provide powerful measures of disease outcome.