Sciatic nerve enlargement in the Klippel-Trenaunay-Weber syndrome

The case of a 35-year-old woman with Klippel-Trenaunay-Weber syndrome (KTWS) showing clinical symptoms of a peroneal nerve lesion is presented. An immense nerve enlargement along most of the sciatic, peroneal and tibial nerve was found to be due to a lipoma arising from the epi- and perineurium. Treatment consisted of extensive microsurgical neurolysis and excision of the tumor resulting in decompression of the affected nerves. Although rare, a perineural lipoma should be kept in mind in patients with KTWS showing neurological abnormalities.

Microsurgical repair of the sural nerve after nerve biopsy to avoid associated sensory morbidity: a preliminary report

OBJECTIVE: The purpose of this article is to report our preliminary results regarding microsurgical repair of the sural nerve after nerve biopsy, in an attempt to reduce the well-described sensory morbidity and neuroma formation. METHODS: Three patients with a suspected diagnosis of peripheral neuropathy underwent sural nerve biopsies to establish definitive diagnoses. A 10-mm segment of the sural nerve was resected with local anesthesia. After harvesting of the specimen, the proximal and distal nerve stumps were carefully mobilized and united with epineural suture techniques, under a surgical microscope. Sensory evaluations (assessing the presence of hypesthesia/dysesthesia or pain) of the lateral aspect of the foot, in regions designated Areas 1, 2, and 3, were performed before and 6 and 12 months after the biopsies. A visual analog scale was used for pain estimation. RESULTS: The biopsy material was sufficient for histopathological examinations in all cases, leading to conclusive diagnoses (vasculitis in two cases and amyloidosis in one case). The early post-biopsy hypesthesia, which was present for 4 to 8 weeks, improved to preoperative levels as early as 6 months after the nerve repair. Sensory evaluations performed at 6- and 12-month follow-up times demonstrated that none of the patients complained of pain at the biopsy site or distally in the area innervated by the sural nerve. Ultrasonography performed at the 12-month follow-up examination revealed normal sural nerve morphological features, with no neuroma formation, comparable to findings for the contralateral site. CONCLUSION: Microsurgical repair of the sural nerve after biopsy can eliminate or reduce sensory disturbances such as paraesthesia, hypesthesia, and dysesthesia distal to the biopsy site, in the distribution of the sensory innervation of the sural nerve, and can prevent painful neuroma formation. To our knowledge, this article is the first in the literature to report on microsurgical repair of the sural nerve after nerve biopsy. Decreased side effects suggest that this technique can become a standard procedure after sural nerve biopsy, which is commonly required to establish the diagnosis of various diseases, such as peripheral nerve pathological conditions, vasculitis, and amyloidosis. More cases should be analyzed, however, to explore the usefulness of the technique and the reliability of sural nerve biopsy samples in attempts to obtain conclusive diagnoses.

Comparison between confocal scanning laser tomography, scanning laser polarimetry and optical coherence tomography on the ability to detect localised retinal nerve fibre layer defects in glaucoma patients

BACKGROUND/AIM: To compare the ability of confocal scanning laser tomography (CSLT), scanning laser polarimetry (SLP) and optical coherence tomography (OCT) in recognising localised retinal nerve fibre layer (RNFL) defects. METHODS: 51 eyes from 43 patients with glaucoma were identified by two observers as having RNFL defects visible on optic disc photographs. 51 eyes of 32 normal subjects were used as controls. Three masked observers evaluated CSLT, SLP and OCT images to determine subjectively the presence of localised RNFL defects. RESULTS: Interobserver agreement was highest with OCT, followed by SLP and CSLT (mean kappa: 0.83, 0.69 and 0.64, respectively). RNFL defects were identified in 58.8% of CSLT, 66.7% of SLP and 54.9% of OCT (p = 0.02 between SLP and OCT) by at least two observers. In the controls, 94.1% of CSLT, 84.3% of SLP and 94.1% of OCT scans, respectively, were rated as normal (p = 0.02 between CSLT and SLP, and SLP and OCT). CONCLUSION: Approximately 20-40% of localised RNFL defects identified by colour optic disc photographs are not detected by CSLT, SPL or OCT. SLP showed a higher number of false-positive results than the other techniques, but also had a higher proportion of correctly identified RNFL defects in the glaucoma population.

Effect of discharge desynchronization on the size of motor evoked potentials: an analysis

OBJECTIVE: Motor evoked potentials (MEPs) after transcranial magnetic brain stimulation (TMS) are smaller than CMAPs after peripheral nerve stimulation, because desynchronization of the TMS-induced motor neurone discharges occurs (i.e. MEP desynchronization). This desynchronization effect can be eliminated by use of the triple stimulation technique (TST; Brain 121 (1998) 437). The objective of this paper is to study the effect of discharge desynchronization on MEPs by comparing the size of MEP and TST responses. METHODS: MEP and TST responses were obtained in 10 healthy subjects during isometric contractions of the abductor digiti minimi, during voluntary background contractions between 0% and 20% of maximal force, and using 3 different stimulus intensities. Additional data from other normals and from multiple sclerosis (MS) patients were obtained from previous studies. RESULTS: MEPs were smaller than TST responses in all subjects and under all stimulating conditions, confirming the marked influence of desynchronization on MEPs. There was a linear relation between the amplitudes of MEPs vs. TST responses, independent of the degree of voluntary contraction and stimulus intensity. The slope of the regression equation was 0.66 on average, indicating that desynchronization reduced the MEP amplitude on average by one third, with marked inter-individual variations. A similar average proportion was found in MS patients. CONCLUSIONS: The MEP size reduction induced by desynchronization is not influenced by the intensity of TMS and by the level of facilitatory voluntary background contractions. It is similar in healthy subjects and in MS patients, in whom increased desynchronization of central conduction was previously suggested to occur. Thus, the MEP size reduction observed may not parallel the actual amount of desynchronization.

Enhancing rehabilitation of motor deficits with peripheral nerve stimulation

A number of different neurorehabilitation strategies include manipulation of the somatosensory system, e.g. in the form of training by passive movement. Recently, peripheral electrical nerve stimulation has been proposed as a simple, painless method of enhancing rehabilitation of motor deficits. Several physiological studies both in animals and in humans indicate that a prolonged period of patterned peripheral electrical stimulation induces short-term plasticity at multiple levels of the motor system. Small-scale studies in humans indicate that these plastic changes are linked with improvement in motor function, particularly in patients with chronic motor deficits after stroke. Somatosensory-mediated disinhibition of motor pathways is a possible underlying mechanism and might explain why peripheral electrical stimulation is more effective when combined with active training. Further large-scale studies are needed to identify the optimal stimulation protocol and the patient groups that stand to benefit the most from this technique.

Improvement in cardiac sympathetic nerve activity in responders to resynchronization therapy

AIMS: To assess changes in cardiac adrenergic activity with cardiac resynchronization therapy (CRT), and to investigate whether these changes are related to improvement in left ventricular ejection fraction (LVEF). METHODS AND RESULTS: Sixteen patients (13 males, age 66 +/- 7 years) were studied at baseline and after > or =6 months of CRT (mean follow-up 9.2 +/- 3.2 months). LVEF was assessed by nuclear angiography. Responders were defined as patients showing > or =5% absolute increase in LVEF + improvement in > or =1 NYHA class + absence of heart failure hospitalization. Cardiac sympathetic nerve activity was studied by (123)I-metaiodobenzyl-guanidine ((123)I-MIBG) scintigraphy. Responders (n = 8) showed lower (123)I-MIBG washout at follow-up when compared with non-responders (P = 0.002), indicating lower cardiac sympathetic nerve activity. The decrease in (123)I-MIBG washout at follow-up when compared with baseline was only seen in the responder group (P = 0.036). There was a moderate correlation between increase in LVEF and decrease in (123)I-MIBG washout (r = 0.52, P = 0.04). CONCLUSION: CRT induces a reduction in cardiac sympathetic nerve activity in responders, that parallels an improvement in LVEF, whereas non-responders do not show any significant changes.

[Interradicular course of the inferior alveolar nerve at the mandibular right third molar and monostotic fibrous dysplasia affecting the mandibular left third molar in the same patient. A case report]

To minimize the risk of intraoperative complications, a comprehensive radiological diagnostic work-up should be a routine procedure in oral surgery. This is especially true concerning possible damage to the inferior alveolar nerve during surgical removal of the third molars. The course and location of the nerve are best assessed when evaluating panoramic view images or cone beam CTs. The following case report demonstrates and discusses the importance of a thorough radiological evaluation before surgery, the problems raised by an interradicular course of the inferior alveolar nerve, and the finding of a monostotic fibrous dyplasia in the same patient.

Corticospinal output and loss of force during motor fatigue

The objective of this study was to analyze central motor output changes in relation to contraction force during motor fatigue. The triple stimulation technique (TST, Magistris et al. in Brain 121(Pt 3):437-450, 1998) was used to quantify a central conduction index (CCI = amplitude ratio of central conduction response and peripheral nerve response, obtained simultaneously by the TST). The CCI removes effects of peripheral fatigue from the quantification. It allows a quantification of the percentage of the entire target muscle motor unit pool driven to discharge by a transcranial magnetic stimulus. Subjects (n = 23) performed repetitive maximal voluntary contractions (MVC) of abductor digiti minimi (duration 1 s, frequency 0.5 Hz) during 2 min. TST recordings were obtained every 15 s, using stimulation intensities sufficient to stimulate all cortical motor neurons (MNs) leading to the target muscle, and during voluntary contractions of 20% of the MVC to facilitate the responses. TST was also repetitively recorded during recovery. This basic exercise protocol was modified in a number of experiments to further characterize influences on CCI of motor fatigue (4 min exercise at 50% MVC; delayed fatigue recovery during local hemostasis, "stimulated exercise" by 20 Hz trains of 1 s duration at 0.5 Hz during 2 min). In addition, the cortical silent period was measured during the basic exercise protocol. Force fatigued to approximately 40% of MVC in all experiments and in all subjects. In all subjects, CCI decreased during exercise, but this decrease varied markedly between subjects. On average, CCI reductions preceded force reductions during exercise, and CCI recovery preceded force recovery. Exercising at 50% for 4 min reduced muscle force more markedly than CCI. Hemostasis induced by a cuff delayed muscle force recovery, but not CCI recovery. Stimulated exercise reduced force markedly, but CCI decreased only marginally. Summarized, force reduction and reduction of the CCI related poorly quantitatively and in time, and voluntary drive was particularly critical to reduce the CCI. The fatigue induced reduction of CCI may result from a central inhibitory phenomenon. Voluntary muscle activation is critical for the CCI reduction, suggesting a primarily supraspinal mechanism.

Minimal local anesthetic volume for peripheral nerve block: a new ultrasound-guided, nerve dimension-based method

BACKGROUND AND OBJECTIVES: Nerve blocks using local anesthetics are widely used. High volumes are usually injected, which may predispose patients to associated adverse events. Introduction of ultrasound guidance facilitates the reduction of volume, but the minimal effective volume is unknown. In this study, we estimated the 50% effective dose (ED50) and 95% effective dose (ED95) volume of 1% mepivacaine relative to the cross-sectional area of the nerve for an adequate sensory block. METHODS: To reduce the number of healthy volunteers, we used a volume reduction protocol using the up-and-down procedure according to the Dixon average method. The ulnar nerve was scanned at the proximal forearm, and the cross-sectional area was measured by ultrasound. In the first volunteer, a volume of 0.4 mL/mm of nerve cross-sectional area was injected under ultrasound guidance in close proximity to and around the nerve using a multiple injection technique. The volume in the next volunteer was reduced by 0.04 mL/mm in case of complete blockade and augmented by the same amount in case of incomplete sensory blockade within 20 mins. After 3 up-and-down cycles, ED50 and ED95 were estimated. Volunteers and physicians performing the block were blinded to the volume used. RESULTS: A total 17 of volunteers were investigated. The ED50 volume was 0.08 mL/mm (SD, 0.01 mL/mm), and the ED95 volume was 0.11 mL/mm (SD, 0.03 mL/mm). The mean cross-sectional area of the nerves was 6.2 mm (1.0 mm). CONCLUSIONS: Based on the ultrasound measured cross-sectional area and using ultrasound guidance, a mean volume of 0.7 mL represents the ED95 dose of 1% mepivacaine to block the ulnar nerve at the proximal forearm.