Delayed complications of deep brain stimulation: 16-year experience in 249 patients.

BACKGROUND: Over the years, most of the deep brain stimulation (DBS) complications described have been mainly related to the surgery itself or the stimulation. Only a few authors have dealt with chronic complications or complications due to implanted material. METHODS: We retrospectively analyzed complications beyond the 1st month after surgery in 249 patients undergoing DBS at our site for 16 years, with 321 interventions overall. RESULTS: Our results show that infection is the most frequent delayed complication (12.5%), the pulse generator being the most common location. Lead breaks (9.3%) are the second most frequent complication. Symptomatic peri-lead edema and cyst formation were exceptional. CONCLUSIONS: The best knowledge about DBS complications allows for better solutions. In case of infection, conservative treatment or partial removal of the DBS system appears to be safe and reasonable. Intracranial complications related to DBS material such as peri-lead edema and cyst formation have a good prognosis. They may appear long after DBS implantation.

Bilateral pallidal deep brain stimulation in myoclonus-dystonia: our experience in three cases and their follow-up.

BACKGROUND: Myoclonus-dystonia syndrome (MDS) is an autosomal dominant movement disorder caused by mutations in the SGCE gene. MDS is characterized by mild dystonia and myoclonic jerks, and a constellation of psychiatric manifestations. Deep brain stimulation (DBS) of bilateral internal globus pallidus (GPi) has recently been introduced as a new and beneficial technique to improve motor symptoms in MDS. METHODS: We report three proven genetically MDS cases with successful response to DBS, and their clinical evolution over years. RESULTS: DBS improves significantly the Unified Myoclonus Rating Scale and Burke-Fahn-Marsden Dystonia Rating Scale in all three patients. This improvement is sustained over the years and no major adverse events were recorded. DBS stimulation parameters employed are justified and compared with cases reported throughout the literature. DISCUSSION: DBS of bilateral GPi is an effective and safe therapy to be considered in MDS refractory cases. Careful neuropsychological evaluation is essential inside the presurgery planning. Correct location of the DBS electrodes and individualized selection of stimulation parameters in each case are the main determinants of the best clinical response.

[Recommendations for the clinical use of motor evoked potentials in multiple sclerosis]. / Recomendaciones para la utilización clínica del estudio de potenciales evocados motores en la esclerosis múltiple.

OBJECTIVE: To establish clinical guidelines for the clinical use and interpretation of motor evoked potentials (MEP) in diagnosing and monitoring patients with multiple sclerosis (MS). Recommendations for MEP use and interpretation will help us rationalise and optimise resources used in MS patient diagnosis and follow up. METHOD: We completed an extensive literature review and pooled our own data to produce a consensus statement with recommendations for the clinical use of MEPs in the study of MS. RESULTS: MEPs, in addition to spinal and cranial magnetic resonance imaging (MRI), help us diagnose and assess MS patients whose disease initially presents as spinal cord syndrome and those with non-specific brain MRI findings, or a normal brain MRI and clinical signs of MS. CONCLUSIONS: Whenever possible, a multimodal evoked potential study should be performed on patients with suspected MS in order to demonstrate involvement of the motor pathway which supports a diagnosis of dissemination in space.

Receptive field asymmetries and sensitivity to random dot stereograms.

The differences between the two monocular receptive fields of cortical cells were measured and compared to their disparity tuning in the awake behaving monkey. Several receptive field properties (direction selectivity, orientation preference, eye preference and response modulation) were determined for each eye using sweeping bright bars. The disparity sensitivity of these cells was also assessed by plotting their response profile, determined for each cell under strictly binocular cyclopean stimulation (dynamic random dot stereograms, RDS). We have found that large differences between the two monocular receptive fields were infrequent and, apparently, not related with the disparity sensitivity profile. We conclude that the monocular asymmetries tested in this study and the sensitivity to positional binocular disparities present in RDS, might be linked to different mechanisms involved in depth perception in the visual system.

Cell responses to vertical and horizontal retinal disparities in the monkey visual cortex.

Because of the horizontal separation of both ocular globes, the projection angles are slightly different. These differences are commonly termed retinal disparities. Vertical and horizontal retinal disparities occur constantly in normal life. We have investigated the responses of single cells in cortical areas V1 and V2 of behaving Macaca mulatta monkeys to retinal disparities by using dynamic random dot stereograms. Our findings show that cortical visual cells are sensitive to both vertical and horizontal disparities. To calculate the distance between two objects in a three-dimensional space from horizontal disparities, it is necessary to know the fixation distance. It has been suggested that the horizontal gradient of vertical disparity contains information to estimate the fixation distance and therefore to scale horizontal disparities. We suggest that these cells sensitive to horizontal and vertical disparities represent a neural mechanism that provides information to the visual system in order to achieve a correct eye alignment and depth perception.

Electroretinographic changes during childhood and adolescence.

Electroretinogram (ERG) changes with age have been studied widely, but there is no general agreement about the age at which ERG parameters reach adult values. We studied 296 eyes from 148 healthy subjects, divided into 14 age groups, ranging from 1 week to 21 years. Although most of the maturational changes or ERG take place during the first six months, the a wave completes development at three years of age and the b component shows a smooth increase in latency between 3 and 18-21 years. The latter component also shows an increase in amplitude from 7-8 to 12-14 years. During the first period of maturation the b wave parameters follow a multiplicative model. These data are discussed in relation to previously reported findings on ERG maturation and to morphological and functional eye changes with age.

Fos expression in the trigeminal sensory nuclei after a chemical lesion of the lower lip mucosa.

C-fos containing neurons were investigated in the trigeminal sensory nuclear complex and in the dorsal horns of the cervical spinal cord (C1-C2) of the rat after a chemical noxious stimulus was applied to the lower lip mucosa. Numerous labelled neuronal nuclei were detected in the dorsolateral area of the caudal half of the trigeminal nucleus interpolaris, and in Rexed's laminae I-IIo of the dorsomedial area of the trigeminal nucleus caudalis and rostral C1. A few c-fos-labelled neurons were observed in laminae IIi and V. No Fos expression was detected in the trigeminal oral and principal nuclei.

Somatosensory responses in the cat motor cortex. I. Identification and course of an afferent pathway.

1. The main aim of the present series of experiments was to demonstrate with electrophysiological methods that the spinothalamocortical system may send somesthetic information to the pyramidal and corticospinal tract cells in the motor cortex of the cat. 2. Experiments were carried out on acutely prepared cats anesthetized with alpha-chloralose. Extra- and intracellular recordings were made from the cells located in the pericruciate motor cortex (the lateral portion of area 4 gamma). They were identified by their antidromic responses to pyramidal stimulation and/or stimulation of the dorsolateral funiculus of the spinal cord. The animals were subjected to a set of nervous tissue lesions to prevent any transit of extereoceptive information to the motor cortex via the cerebellum and the somatosensory cortex. A lesion of the dorsal part of the spinal cord was also made, leaving intact only the afferent inflow ascending in the spinal ventral half, i.e., the spinothalamic system. 3. In this cat preparation it was observed that both electrical and natural stimulation of the limbs still efficiently activated the motor cortical efferent cells. 4. The pathway was mapped by applying microstimulation along its whole course in the spinal cord and brain stem. Stimulation of the primary afferent fibers running in the dorsal columns caudally to the spinal cord lesion produced activation and/or inhibition of the cortical cells. The existence of these responses may be attributable to the existence of collaterals from primary afferent fibers located in the dorsal columns, which activate the spinothalamic tract cells either mono- or polysynaptically. In the brain stem the fibers join the medial lemniscus. 5. In view of the short latency of the responses (mean latency 10.5 ms from the spinal cord) it is suggested that this component of the spinothalamic system may play an important role in the sensory regulation of ongoing movements.

Short latency somaesthetic responses in motor cortex, transmitted through the spino-thalamic system, in the cat.

Evidence is presented that in the cat, the spinothalamic system contributes to short latency somaesthetic responses in motor cortex efferent cells. Intracellular recordings performed on identified pyramidal tract cells and corticospinal cells show that these cells are still activated and/or inhibited from the periphery after a set of central nervous lesions leaving intact only the ventral half of the spinal cord. The responses were attributed to the spinothalamic system. The ascending system is activated through collaterals of afferent fibres running in the dorsal columns of the spinal cord. This peripheral link to the motor cortex might participate in updating the motor command on the basis of information feedback from the periphery.

A common somaesthetic pathway to red nucleus and motor cortex.

Comparable short latency somaesthetic responses have been observed in the red nucleus and the motor cortex. Since previous experiments showed that a ventral spinal ascending pathway could account for red nucleus responses, the present experiments were designed to establish whether the same pathway could also transmit the short latency peripheral inputs to motor cortex. Two experimental data argue in favour of a such organization: (1) Using the collision technique, it was demonstrated that somaesthetic responses recorded in red nucleus cells are transmitted by collaterals of ascending fibres ending in the ventrobasal thalamus. (2) Intracellular recordings from identified corticospinal cells were performed on cats acutely prepared on section of the brachium conjunctivum and the dorsal columns of the spinal cord. Cortico-cortical connections to motor cortex were also eliminated by lesions of the ipsilateral sensory cortex and contralateral motor cortex. With this preparation it is still possible to record postsynaptic potentials after stimulation of primary afferent fibres in the dorsal columns, caudally to their section. The existence of these somaesthetic parallel inputs to rubro- and corticospinal cells suggest that the ongoing movement might be corrected on-line by these two pathways.