Biomedical subjects

R Birch

Publications and source records attributed to R Birch.

At least 37 records · Page 2Linked to original sources

PubMed2002

Restoration of sensory function and lack of long-term chronic pain syndromes after brachial plexus injury in human neonates.

Obstetric complications are a common cause of brachial plexus injuries in neonates. Failure to restore sensation leads to trophic injuries and poor limb function. It is not known whether the infant suffers chronic neuropathic or spinal cord root avulsion pain; in adults, chronic pain is usual after spinal root avulsion injuries, and this is often intractable. The plexus is repaired surgically in severe neonatal injures; if no spontaneous recovery has occurred by 3 months, and if neurophysiological investigations point to poor prognosis, then nerve trunk injures are grafted, while spinal cord root avulsion injuries are treated by transferring an intact neighbouring nerve (e.g. intercostal) to the distal stump of the damaged nerve, in an attempt to restore sensorimotor function. Using a range of non-invasive quantitative measures validated in adults, including mechanical, thermal and vibration perception thresholds, we have assessed for the first time sensory and cholinergic sympathetic function in 24 patients aged between 3 and 23 years, who had suffered severe brachial plexus injury at birth. While recovery of function after spinal root avulsion was related demonstrably to surgery, there were remarkable differences from adults, including excellent restoration of sensory function (to normal limits in all dermatomes for at least one modality in 16 out of 20 operated cases), and evidence of exquisite CNS plasticity, i.e. perfect localization of restored sensation in avulsed spinal root dermatomes, now presumably routed via nerves that had been transferred from a distant spinal region. Sensory recovery exceeded motor or cholinergic sympathetic recovery. There was no evidence of chronic pain behaviour or neuropathic syndromes, although pain was reported normally to external stimuli in unaffected regions. We propose that differences in neonates are related to later maturation of injured fibres, and that CNS plasticity may account for their lack of long-term chronic pain after spinal root avulsion injury.

Adolescent↗

PubMed2002

Calcium-activated potassium channel SK1- and IK1-like immunoreactivity in injured human sensory neurones and its regulation by neurotrophic factors.

Calcium-activated potassium ion channels SK and IK (small and intermediate conductance, respectively) may be important in the pathophysiology of pain following nerve injury, as SK channels are known to impose a period of reduced excitability after each action potential by afterhyperpolarization. We studied the presence and changes of human SK1 (hSK1)- and hIK1-like immunoreactivity in control and injured human dorsal root ganglia (DRG) and peripheral nerves and their regulation by key neurotrophic factors in cultured rat sensory neurones. Using specific antibodies, hSK-1 and hIK-1-like immunoreactivity was detected in a majority of large and small/medium-sized cell bodies of human DRG. hSK1 immunoreactivity was decreased significantly in cell bodies of avulsed human DRG (n = 8, surgery delay 8 h to 12 months). There was a decrease in hIK1-like immunoreactivity predominantly in large cells acutely (<3 weeks after injury), but also in small/medium cells of chronic cases. Twenty-three injured peripheral nerves were studied (surgery delay 8 h to 12 months); in five of these, hIK1-like immunoreactivity was detected proximally but not distally to injury, whereas neurofilament staining confirmed the presence of nerve fibres in both regions. These five nerves, unlike the others, had all undergone Wallerian degeneration previously and the loss of hIK1-like immunoreactivity may therefore reflect reduced axonal transport of this ion channel across the injury site in regenerated fibres, as well as decreased expression in the cell body. In vitro studies of neonatal rat DRG neurones showed that nerve growth factor (NGF) significantly increased the percentage of hSK1-positive cells, whereas neurotrophin 3 (NT-3) and glial cell line-derived neurotrophic factor (GDNF) failed to show a significant effect. NT-3 stimulated hIK1 expression, while NGF and GDNF were ineffective. As expected, NGF increased expression of the voltage-gated sodium channel SNS1/PN3 in this system. Decreased retrograde transport of these neurotrophic factors in injured sensory neurones may thus reduce expression of these ion channels and increase excitability. Blockade of IK1-like and other potassium channels by aminopyridines (4-AP and 3,4-DAP) may also explain the paraesthesiae induced by these medications. Selective potassium channel openers are likely to represent novel therapies for pain following nerve injury.

Adult↗

PubMed2002

Ultrasound diagnosis of shoulder congruity in chronic obstetric brachial plexus palsy.

Ultrasound (US) was used to determine the congruity of the shoulder in 22 children with a deformity of the shoulder secondary to chronic obstetric brachial plexus palsy. There were 11 boys and 11 girls with a mean age of 4.75 years (0.83 to 13.92). The shoulder was scanned in the axial plane using a posterior approach with the arm internally rotated. The humeral head was classified as being either congruent or incongruent. The US appearance was compared with that on clinical examination and related to the intraoperative findings. All 17 shoulders diagnosed as incongruent on US were found to be incongruent at operation, whereas three diagnosed as congruent by US were found to be incongruent at operation. The diagnostic accuracy of US for the identification of shoulder incongruity was 82% when compared with the findings at surgery. US is a valuable, but not infallible tool, for the detection of incongruity of the shoulder.

Adolescent↗

PubMed2001

Long-term trans-synaptic glial responses in the human thalamus after peripheral nerve injury.

Limb denervation leads to reorganization of the representational zones of the somatosensory cortex. Using [11C](R)-PK11195, a sensitive in vivo marker of glial cell activation, and PET, we provide first evidence that limb denervation induces a trans-synaptic increase in [11C](R)-PK11195 binding in the human thalamus but not somatosensory cortex: these brain structures appeared morphologically normal on magnetic resonance imaging (MRI). The increased thalamic signal was detectable many years after nerve injury, indicating persistent reorganization of the thalamus. This glial activation, beyond the first-order projection area of the injured neurons, may reflect continually altered afferent activity. Our findings support the view that long-term rearrangement of cortical representational maps is significantly determined within the thalamus.

Adult↗

PubMed2001

Sodium channel beta1 and beta2 subunits parallel SNS/PN3 alpha-subunit changes in injured human sensory neurons.

Voltage-gated sodium channels consist of a pore-containing alpha-subunit and one or more auxiliary beta-subunits, which may modulate channel function. We previously demonstrated that sodium channel SNS/PN3 alpha-subunits were decreased in human sensory cell bodies after spinal root avulsion injury, and accumulated at injured nerve terminals in pain states. Using specific antibodies for immunohistochemistry, we have now detected sodium channel beta1 and beta2 subunits in sensory cell bodies within control human postmortem sensory ganglia (78% of small/medium (< or = 50 microm) and 68% of large (> or = 50 microm) cells); their changes in cervical sensory ganglia after avulsion injury paralleled those described for SNS/PN3 alpha-subunits. Our results suggest that alpha- and beta-subunits share common regulatory mechanisms, but present distinct targets for novel analgesics.

Adult↗

PubMed2001

Plasticity of TTX-sensitive sodium channels PN1 and brain III in injured human nerves.

Sensory neurones co-express voltage-gated sodium channels that mediate TTX-sensitive (TTX-S) and TTX-resistant (TTX-R) currents, which may contribute to chronic pain after nerve injury. We previously demonstrated that TTX-R channels were decreased acutely in human sensory cell bodies after central axotomy, but accumulated in nerve terminals after peripheral axotomy. We have now studied the TTX-S channels PN1 and Brain III, using specific antibodies for immunohistochemistry, in dorsal root ganglia (DRG) from 10 patients with traumatic central axotomy, nerves from 16 patients with peripheral axotomy, and controls. PN1 showed temporal changes similar to the TTX-R channels in sensory cell bodies of injured DRG. In contrast, Brain III was found only in injured nerves (not control nerves, or control/central axotomy DRG). PNI and Brain III are distinct targets for novel analgesics.

Adult↗

PubMed2001

Morphology of rsw1, a cellulose-deficient mutant of Arabidopsis thaliana.

The rsw1 mutant of Arabidopsis thaliana is mutated in a gene encoding a cellulose synthase catalytic subunit. Mutant seedlings produce almost as much cellulose as the wild type at 21 degrees C but only about half as much as the wild type at 31 degrees C. We used this conditional phenotype to investigate how reduced cellulose production affects growth and morphogenesis in various parts of the plant. Roots swell in all tissues at 31 degrees C, and temperature changes can repeatedly switch them between swollen and slender growth patterns. Dark-grown hypocotyls also swell, whereas cotyledons and rosette leaf blades are smaller, their surfaces are more irregular and their petioles shorter. Leaf trichomes swell and branch abnormally. Plants readily initiate inflorescences at 31 degrees C which have shorter but not fatter bolts and stomata which bulge above the uneven surface of internodes. Bolts carry the normal number of flowers, but their stigmas protrude beyond the shortened sepals and petals. Anthers dehisce normally, but self-fertilisation is reduced because the stigma is well above the anthers. Anther filaments are short and show a crumpled surface. Viable pollen develops, but female reproductive competence and postpollination development are severely impaired. We conclude that the RSW1 gene is important for cellulose synthesis in many parts of the plant and that reduced cellulose synthesis suppresses organ expansion rather than organ initiation, causes radial swelling only in the root and hypocotyl, but makes the surfaces of many organs uneven. We discuss some possible reasons to explain why different organs vary in their responses. The morphological changes suggest that RSW1 contributes cellulose to primary walls but do not yet exclude a role during secondary-wall deposition.

Arabidopsis↗

PubMed2001

Long-term results of tibialis posterior tendon transfer for drop-foot.

Twelve patients with drop-foot secondary to sciatic or common peroneal nerve palsy treated with transfer of the tibialis posterior tendon were followed-up for a mean of 90 (24-300) months. In 10 patients the results were 'excellent' or 'good'. In 11 patients grade 4 or 5 power of dorsiflexion was achieved, although the torque, as measured with a Cybex II dynamometer, and generated by the transferred tendon, was only about 30% of the normal side. Seven patients were able to dorsiflex their foot to the neutral position and beyond. The results appeared to be better in men under 30 years of age with common peroneal palsies. A painful flatfoot acquired in adulthood does not appear to be a significant long-term complication despite the loss of a functioning tibialis posterior tendon.

Adolescent↗

PubMed2001

Immunolocalisation of sodium channel NaG in the intact and injured human peripheral nervous system.

The voltage-gated 'glial' sodium channel NaG belongs to a distinct molecular class within the multi-gene family of mammalian sodium channels. Originally found in central and peripheral glia, NaG has since been detected in neurons in rat dorsal root ganglia (DRG) and may play a role in Schwann cell-axon interactions. We have studied the presence of NaG-like immunoreactivity in the intact and injured human peripheral nervous system using a specific affinity-purified antibody. Nerve fibres in normal and injured peripheral nerves and normal skin exhibited intense NaG-immunoreactivity. Numerous NaG-immunoreactive nerve fibres surrounded neuronal cell bodies within postmortem control DRG, and in DRG avulsed from the spinal cord (i.e. after traumatic central axotomy). There were no significant differences in the pattern of NaG immunostaining between control and avulsed DRG, or with delay after injury. Generally, the neuronal cell bodies were only very weakly immunoreactive to NaG, indicating that the NaG immunoreactivity was predominantly in Schwann cells/myelin. In accord, we demonstrated NaG immunostaining in cultured human and rat Schwann cells, and in distal nerve after wallerian degeneration. NaG thus appears to be a useful new marker for Schwann cells in the human PNS, and a role in neuropathy deserves investigation.

Animals↗

PubMed2001

Imaging of adult brachial plexus traction injuries.

Closed, high-energy transfer traction injuries of the adult brachial plexus lead to rupture or avulsion of the spinal nerves. Accurate preoperative diagnosis is crucial for surgical planning and reconstruction. Myelography, computerised tomographic myelography and magnetic resonance imaging are the main radiological methods for preoperative diagnosis of the lesion. This article reviews the current status of imaging of traction injuries of the adult brachial plexus.

Adult↗

PubMed2001

A method for evaluating the results of tendon transfers for foot drop.

A system for assessing the results of tibialis posterior tendon transfers in the treatment of foot drop secondary to nerve palsy is proposed. There are seven sections to this scoring system: pain, need for orthosis, ability to wear normal shoes, activity level, muscle power of ankle dorsiflexion, degree of active ankle dorsiflexion, and foot posture. The total score is 100. The results are classified as excellent for scores between 85 and 100, good between 70 and 84, fair between 55 and 69, and poor for scores below 55. The results of 18 patients (mean followup, 64.6 months) who had a tibialis posterior tendon transfer were assessed using this method. Four patients (22.2%) had an excellent result, seven (38.8%) had a good result, two (11.1%) had a fair result, and five (27.7%) had a poor result. The average score was 67.2, suggesting an overall fair result for this operation. In nine patients, there was correlation between the outcome when assessed with this method and with patient rating. In two patients, the outcomes were better when assessed with this method than with patient rating, whereas the reverse was true in seven other patients. Thus, this system may provide a more objective and critical evaluation of tibialis posterior transfers for foot drop.

Adolescent↗

PubMed2001

Increased acid-sensing ion channel ASIC-3 in inflamed human intestine.

OBJECTIVES: Acid-sensing ion channels (ASICs) are expressed by rat sensory neurons and may mediate pain associated with tissue acidosis after inflammation or injury. Our aim was to examine the molecular forms and localization of ASICs in human intestine and dorsal root ganglia using immunochemical techniques, and to measure the effects of inflammation and injury. DESIGN AND METHODS: Inflamed Crohn's disease intestine and injured human dorsal root ganglia, with appropriate controls, were studied by Western blotting and immunohistochemistry, using specific affinity-purified ASIC antibodies. RESULTS: In the Western blot, there was a significant three-fold increase in the mean relative optical density of the ASIC-3 55-kDa band (but not ASIC-1 or ASIC-2) in full-thickness inflamed intestine, as well as in separated muscle and mucosal layers. There was a corresponding trend for an increased immunoreactive density and increased number of ASIC-3-positive neurons in the myenteric and sub-mucous plexus of inflamed intestine. In dorsal root ganglia, immunoreactivity for all ASICs was restricted to a sub-population (about 50%) of small-diameter (nociceptor) sensory neurons, and was generally less intense after injury. CONCLUSIONS: Increased ASIC-3 in inflamed intestine suggests a role in pain or dysmotility, for which ASICs represent new therapeutic targets.

Acid Sensing Ion Channels↗

PubMed2001

Rupture of the axillary (circumflex) nerve and artery in a champion jockey.

Rupture of the circumflex artery and nerve, without fracture or dislocation, is a rare traumatic event. Such a case is reported in a champion flat jockey who sustained blunt trauma to the shoulder after a fall during a race; the literature is also reviewed. At urgent surgical exploration, the axillary artery and nerve were repaired. The patient subsequently successfully returned to professional riding. This case highlights the difficulties in diagnosis and management.

Adult↗

PubMed2001

Tibialis posterior tendon dysfunction: a primary or secondary problem?

Seventeen patients with a mean follow-up of 64.4 months following a tibialis posterior tendon transfer to regain active foot dorsiflexion were clinically examined specifically for signs of tibialis posterior tendon dysfunction. The results show that 8 patients (47%) had Grade 4 or better power of eversion but none had a clinical flatfoot on the Harris-Beath footprints. Only 6% had forefoot abduction; 17% exhibited hindfoot valgus and 82% were able to perform the single-heel rise. Tibialis posterior tendon dysfunction therefore does not appear to be an inevitable sequel of tibialis posterior tendon transfer even in the presence of a functioning peroneal muscle. Other studies have noted that a pre-existent flatfoot was often present in patients with tibialis posterior tendon dysfunction. None of the patients in this study had pre-existent flatfoot. We suggest that a predisposition, in the form of a pre-existent tendency to flatfoot may also be a factor in the pathogenesis of tibialis posterior tendon dysfunction. This may explain the long-term failure of flexor digitorum longus and flexor hallucis longus tendon transfers in the treatment for tibialis posterior tendon dysfunction when the biomechanics of the foot has not been altered.

Adolescent↗

PubMed2001

Penetrating missile injuries of the brachial plexus.

We studied a consecutive series of 58 patients with penetrating missile injuries of the brachial plexus to establish the indications for exploration and review the results of operation. At a mean of 17 weeks after the initial injury, 51 patients were operated on for known or suspected vascular injury (16), severe persistent pain (35) or complete loss of function in the distribution of one or more elements of the brachial plexus (51). Repair of the nerve and vascular lesions abolished, or significantly relieved, severe pain in 33 patients (94%). Of the 36 patients who underwent nerve graft of one or more elements of the plexus, good or useful results were obtained in 26 (72%). Poor results were observed after repairs of the medial cord and ulnar nerve, and in patients with associated injury of the spinal cord. Neurolysis of lesions in continuity produced good or useful results in 21 of 23 patients (91%). We consider that a vigorous approach is justified in the treatment of penetrating missile injury of the brachial plexus. Primary intervention is mandatory when there is evidence of a vascular lesion. Worthwhile results can be achieved with early secondary intervention in patients with debilitating pain, failure to progress and progression of the lesion while under observation. There is cause for optimism in nerve repair, particularly of the roots C5, C6 and C7 and of the lateral and posterior cords, but the prognosis for complete lesions of the plexus associated with damage to the cervical spinal cord is particularly poor.

Adolescent↗

PubMed2001

The radial and posterior interosseous nerves. Results fo 260 repairs.

The outcome of 260 repairs of the radial and posterior interosseous nerves, graded by Seddon's modification of the Medical Research Council Special Committee's system, was analysed according to four patterns of injury; open 'tidy', open 'untidy', closed traction, and those associated with injury to the axillary or brachial artery. We studied the effect on the outcome of delay in effecting repair and of the length of the defect in the nerve trunk. Of the 242 repairs of the radial nerve we found that 30% had good results and 28% fair; 42% of the repairs had failed. The violence of injury was the most important factor in determining the outcome. Of the open 'tidy' repairs, 79% achieved a good or fair result, and 36% of cases with arterial injury also reached this level. Most repairs failed when the defect in the nerve trunk exceeded 10 cm. When the repairs were carried out within 14 days of injury, 49% achieved a good result; only 28% of later repairs did so. All repairs undertaken after 12 months failed. Of the 18 repairs of the posterior interosseous nerve, 16 achieved a good result.

Adolescent↗

PubMed2001

Diagnosis of the level of intradural rupture of the rootlets in transaction lesions of the brachial plexus.

The precise point of intradural rupture in preganglionic traction injuries to the brachial plexus has been a subject of controversy. In this study of avulsed roots we have shown that rupture occurs at varying levels. True avulsion of the root with attached spinal cord tissue was seen in two cases and in the remainder rupture was peripheral to the central-peripheral transition zone. We have further shown that corpora amylacea marked the boundary between tissue of the central and peripheral nervous systems. This observation provides a basis for renewed work towards the direct repair of intradural ruptures of the ventral and dorsal roots.

Adult↗

PubMed2001

Latropathic injuries of peripheral nerves.

This is a retrospective study of 612 cases of iatropathic injury to peripheral nerves seen in one tertiary referral unit between 1991 and 1998. A total of 291 patients was subsequently operated on to explore the nerve lesion. The most common presenting symptom was pain, which often masked underlying loss of function. The delay in diagnosis was up to 40 months. The findings at operation were analysed according to the type of nerve damaged, the nature of the injury and the referring specialty. Some of the more common causal operations and procedures are discussed. Preventive measures are listed, and early diagnosis and treatment are recommended.

Adult↗