Stability of the input-output properties of chronically implanted multiple contact nerve cuff stimulating electrodes

The objective of this investigation was to measure the input-output (I-O) properties of chronically implanted nerve cuff electrodes. Silicone rubber spiral nerve cuff electrodes, containing 12 individual platinum electrode contacts, were implanted on the sciatic nerve of seven adult cats for 28-34 weeks. Measurements of the torque generated at the ankle joint by electrical stimulation of the sciatic nerve were made every 1-2 weeks for the first 6 weeks post-implant and every 3-5 weeks between 6 weeks and 32 weeks post-implant. In three implants the percutaneous lead cable was irreparably damaged by the animal within 4 weeks after implant and further testing was not possible. One additional lead cable was irreparably damaged by the animal at 17 weeks post-implant. The three remaining implants functioned for 28, 31, and 32 weeks. Input-output curves of ankle joint torque as a function of stimulus current amplitude were repeatable within an experimental session, but there were changes in I-O curves between sessions. The degree of variability in I-O properties differed between implants and between different contacts within the same implant. After 8 weeks, the session to session changes in the stimulus amplitude required to generate 50% of the maximum torque (I50) were smaller (15+/-19%, mean +/- s.d.) than the changes in I50 measured between 1 week and 8 weeks post-implant (34+/-42%). Furthermore, the I-O properties were more stable across changes in limb position in the late post-implant period than in acutely implanted cuff electrodes. These results suggest that tissue encapsulation acted to stabilize chronically implanted cuff electrodes. Electrode movement relative to the nerve, de- and regeneration of nerve fibers, and the inability to precisely reproduce limb position in the measurement apparatus all may have contributed to the variability in I-O properties.     

Recording properties and biocompatibility of chronically implanted polymer-based intrafascicular electrodes

We implanted polymer-based longitudinal intrafascicular electrodes (polyLIFEs) in feline dorsal rootlets acutely and for periods of two to six months to evaluate their electrical properties and biocompatibility. A total of 38 implanted electrodes were analyzed. Some 25 of the 38 electrodes were implanted with an insulative flexible polymer cuff, which was required for recording of afferent activity in situ. Electrode impedances remained stable for the duration of the experiments. The distributions of axons were measured at three levels of the implanted rootlets: the implant level, 1-2 mm proximal to the implant with respect to the cell body, and 1-2 mm distal to the implant with respect to the cell body. Similar measurements were made in five samples of fascicles neighboring an implant and six samples of control tissue from animals in which no implants were placed. The polyLIFEs demonstrated a high degree of biocompatibility, as no adverse effects on axon size were observed in either the implanted fascicle or neighboring neural tissue. However, the insulative cuffs were found to be a source of compression, resulting in necrosis of the neural tissue.     

Sensory nerve fibres from lumbar intervertebral discs pass through rami communicantes. A possible pathway for discogenic low back pain

It has been thought that lumbar intervertebral discs were innervated segmentally. We have previously shown that the L5-L6 intervertebral disc in the rat is innervated bilaterally from the L1 and L2 dorsal root ganglia through the paravertebral sympathetic trunks, but the pathways between the disc and the paravertebral sympathetic trunks were unknown. We have now studied the spines of 17 rats to elucidate the exact pathways. We examined serial sections of the lumbar spine using immunohistochemistry for calcitonin gene-related peptide, a sensory nerve marker. We showed that these nerve fibres from the intervertebral disc ran through the sinuvertebral nerve into the rami communicantes, not into the corresponding segmental spinal nerve. In the rat, sensory information from the lumbar intervertebral discs is conducted through rami communicantes. If this innervation pattern applies to man, simple decompression of the corresponding nerve root will not relieve discogenic pain. Anterior interbody fusion, with the denervation of rami communicantes, may be effective for such low back pain.     

Loss of large myelinated nerve fibres of the recurrent laryngeal nerve in patients with multiple system atrophy and vocal cord palsy

Prevalence rate and etiology were studied in severely handicapped children of school age in Nagano prefecture as of July, 1994. Severely retarded children were defined as those whose IQ's were lower than 35 and who were unable to walk. The total number of severely retarded children was 165. The prevalence rate was 0.71/1000, 90% of them being in class 1 or 2 of Oshima's classification (bedridden or unable to sit alone and with IQ less than 20), and 26% being cared for at home. Their average gestational age was 38.5 weeks, and the average birthweight 2,772 g. At birth none of them had extremely low birth weight. Etiology of the handicaps was classified as follows; congenital 26.1%; maternal infection 3.0%; prenatal 3.6%; perinatal 27.3%; postnatal 13.9% and unknown 26.1%. Asphyxia decreased gradually but the number of low birth weight premature infants increased. When postnatal etiologies were excluded, the patients with unknown etiology occupied 30.3%, 23.3% of them being light-for-dates baby. The examination of the case histories revealed that causes of unknown etiology are prenatal. If we add unknown etiology to congenital, maternal infection, and prenatal etiology, the prenatal origin is 68%.     

Results of cable graft technique in repair of large nerve trunk lesions

Cable grafting was reintroduced in the beginning of the 1980's as a modified method for repair of large polyfascicular nerves without group arrangement such as trunks and cords of the brachial plexus, sciatic nerve and its divisions, or the other main nerve trunks. We used this method in 25 patients with brachial plexus injury and 29 patients with injuries to the sciatic nerve. Results were analyzed according to the individual nerve elements and were available for 32 elements of the brachial plexus and for 19 tibial and 19 peroneal divisions of the sciatic nerve. We defined useful functional recovery according to the priorities in repair of the brachial plexus and sciatic nerve with lower limits M3 for relevant muscles and functions and S2 for sensory function. Results were especially favourable for the brachial plexus with a total rate of recovery 84% and for tibial division with the same total rate of recovery. On the basis of the results obtained we were able to conclude that the results of the modified cable grafting were at least similar to those of interfascicular nerve grafting and that this method could be useful for repair of large polyfascicular nerve trunks. However, the main advantage of this technique is a considerable gain in operative time.     

A technique for study of lung function in birds by blocking the primary bronchus

The technique described allows in vivo placement of a blocking balloon in the avian primary bronchus between the origins of the two sets of secondary bronchi, the medioventrals and mediodorsals. With caudal air sacs cannulated the animal may then be ventilated with a constant flow of gas passing entirely through the gas-exchanging parabronchi. This technique has been found useful particularly in studies of pulmonary gas exchange in birds.     

Increasing the service life of large graphitized electrodes: A designer's view

GosNIIÉP. Translated from Metallurg, No. 1, pp. 27–28, January, 1989.     

A surgical technique for resecting malignancies invading the facial nerve and petrous pyramid

Certain head and neck malignancies tend to invade branches of the cranial nerves and progress centripetally. The maxillary and mandibular divisions of the V (trigeminal) nerve are the most commonly invaded, but the VII (facial) nerve may harbor extensions of primary parotid malignancies and/or skin cancers originating in or near the ear. Paresis of the VII nerve signifies a serious but not entirely hopeless situation if countered with an appropriate surgical procedure. The optimal treatment of malignancies invading cranial nerves is surgical excision, which may necessitate removal of substantial portions of the cranium. Surgical pursuit of a malignancy in the facial nerve leads to a direct confrontation with the petrous pyramid of the temporal bone. Resection of the petrous pyramide is surgically feasible, but, if performed en bloc, extracts a high morbidity and mortality. An alternate technique in which the soft tissue and bones are removed disjunct is advocated. In this technique, the soft tissues are excised flush with the surface of the temporal bone. After making perforator and burr openings in the squamous temporal bone, a subtotal temporal craniectomy is completed with rongeurs. A prerequisite for success with this technique is the rotation of a large scalp flap and other local flaps to cover the exposed meninges and carotid arteries. A resume of four cases using this technique is presented. The age of the patients, the type, stage, and duration of the malignancies, and other factors which might influence the end stage results are given.     

Rectal neovagina: Simonsen''s technique for large rectovaginal fistula repair

OBJECTIVE: Although trichobezoars are well described in the surgical literature, there is relatively little in the psychiatric literature on them. This study aims to focus the attention of readers on trichobezoars by means of a case report and an overview of the literature. METHOD: We present a case of a patient with trichotillomania and a trichobezoar, including psychiatric management. We also briefly review the relevant literature. RESULTS: Hair-pulling significantly improved in response to treatment with the selective serotonin reuptake inhibitor fluoxetine and supportive psychotherapy. CONCLUSIONS: The medical and psychiatric sequelae of trichotillomania should not be underestimated. Pharmacotherapy may be play a useful role in some patients with this disorder.     

A comparison between control methods for implanted FES hand-grasp systems

Implanted neuroprostheses employing functional electrical stimulation (FES) provide grasp and release to individuals with tetraplegia. This paper describes and compares three methods of controlling the stimulated hand movement: shoulder position, wrist position and myoelectric activity from the wrist extensors. Three experienced neuroprosthesis users were evaluated with each of the control methods by performing a grasp release test (GRT). A significant improvement was found between each functional electrical stimulation (FES) method and tenodesis without FES. No significant difference in overall performance was found between the three FES methods of control. Each method of control demonstrated advantages and disadvantages which depend upon characteristics of the individual patient. Factors which must be considered are injury level, voluntary wrist strength, proximal upper limb strength, the level of cognition of the patient, hand-grasp characteristics, cosmeses, importance of using both arms, and personal preference. Due to the unique characteristics of each controller type, it is advantageous to have each type available for the FES patients to adapt the system to the needs and desires of the individual patient.     

A new technique for sacral nerve stimulation: a percutaneous method for urinary incontinence caused by spinal cord injury

We report a 40-year-old Japanese man with a creeping eruption caused by a larva of the nematode suborder Spirurina type X. He had eaten raw small squid (hotaruika) 4 weeks before the serpiginous erythematous eruption appeared on his abdomen. Routine laboratory tests revealed only slight eosinophilia in his peripheral blood. Although we could not find the larva in an excised skin specimen, an indirect immunofluorescence test confirmed the presence of antibodies against larvae of the suborder Spirurina type X. We review 28 reported cases in Japan which showed that creeping eruption caused by larvae of the suborder Spirurina type X has the following clinical characteristics: an incubation time of 1-4 weeks; a migratory, well-defined, narrow, serpiginous erythematous eruption; and only slight peripheral blood eosinophilia. Excision of the advancing end of the track was curative in our patient.     

Double microcatheter technique for detachable coil treatment of large, wide-necked intracranial aneurysms

We describe a technique used to treat two patients with large, wide-necked aneurysms during the past 2 years. In the initial attempts at embolization, evidence of coil instability within the aneurysm or significant impingement of coil loops on the parent artery was observed. Advancement of a second microcatheter into the aneurysm allowed two coils to be braced across the aneurysmal neck before the detachment of either coil. This technique permitted successful coil treatment in both patients.