Andrew M. Hart

Sensory neuroprotection, mitochondrial preservation, and therapeutic potential of N-acetyl-cysteine after nerve injury

Neuronal death is a major factor in many neuropathologies, particularly traumatic, and yet no neuroprotective therapies are currently available clinically, although antioxidants and mitochondrial protection appear to be fruitful avenues of research. The simplest system involving neuronal death is that of the dorsal root ganglion after peripheral nerve trauma, where the loss of approximately 40% of primary sensory neurons is a major factor in the overwhelmingly poor clinical outcome of the several million nerve injuries that occur each year worldwide. N-acetyl-cysteine (NAC) is a glutathione substrate which is neuroprotective in a variety of in vitro models of neuronal death, and which may enhance mitochondrial protection. Using TdT uptake nick-end labelling (TUNEL), optical disection, and morphological studies, the effect of systemic NAC treatment upon L4 and 5 primary sensory neuronal death after sciatic nerve transection was investigated. NAC (150 mg/kg/day) almost totally eliminated the extensive neuronal loss found in controls both 2 weeks (no treatment 21% loss, NAC 3%, P=0.03) and 2 months after axotomy (no treatment 35% loss, NAC 3%, P=0.002). Glial cell death was reduced (mean number TUNEL positive cells 2 months after axotomy: no treatment 51/ganglion pair, NAC 16/ganglion pair), and mitochondrial architecture was preserved. The effects were less profound when a lower dose was examined (30 mg/kg/day), although significant neuroprotection still occurred. This provides evidence of the importance of mitochondrial dysregulation in axotomy-induced neuronal death in the peripheral nervous system, and suggests that NAC merits investigation in CNS trauma. NAC is already in widespread clinical use for applications outside the nervous system; it therefore has immediate clinical potential in the prevention of primary sensory neuronal death, and has therapeutic potential in other neuropathological systems.

Pharmacological enhancement of peripheral nerve regeneration in the rat by systemic acetyl-L-carnitine treatment

Peripheral nerve trauma remains a major cause of morbidity, largely due to the death of approximately 40% of innervating sensory neurons, and to slow regeneration after repair. Acetyl-L-carnitine (ALCAR) is a physiological peptide that virtually eliminates sensory neuronal death, and may improve regeneration after primary nerve repair. This study determines the effect of ALCAR upon regeneration after secondary nerve repair, thereby isolating its effect upon neuronal regenerative capacity. Two months after unilateral sciatic nerve division 1 cm nerve graft repairs were performed (n=5), and treatment with 50 mg/kg/day ALCAR was commenced for 6 weeks until harvest. Regeneration area and distance were determined by quantitative immunohistochemistry. ALCAR treatment significant increased immunostaining for both nerve fibres (total area 264% increase, P<0.001; percentage area 229% increase, P<0.001), and Schwann cells (total area 111% increase, P<0.05; percentage area 86% increase, P<0.05), when compared to no treatment. Regeneration into the distal stump was greatly enhanced (total area 2,242% increase, P=0.008; percentage area 3,034% increase, P=0.008). ALCAR significantly enhances the regenerative capacity of neurons that survive peripheral nerve trauma, in addition to its known neuroprotective effects.

Shoulder function following autologous latissimus dorsi breast reconstruction. A prospective three year observational study comparing quilting and non-quilting donor site techniques

Latissimus dorsi harvest and axillary surgery can affect shoulder function. The effect of autologous latissimus dorsi flap (ALD) breast reconstruction and donor site quilting have been inadequately studied. A cohort of ALD flap breast reconstruction patients were assessed pre-operatively and at eight post-operative time-points (up to 3 years after reconstruction) using the self-administered Disabilities of the Arm, Shoulder and Hand (DASH) outcome measure, for which validated normative data is available. Patients with incidental shoulder conditions and bilateral reconstructions were excluded. This was a prospective, observational study with blinded data interpretation: 58 patients, 22 of whom had donor site quilting, were assessed. Groups were compatible demographically, in breast care management and in pre-operative DASH score (quilted 6.5, non-quilted 6.4; P=0.98). Scores were significantly increased at initial post-operative clinic review (mean 49, SD19; P<0.001), 6 week (29, SD20; P<0.001), and 3 month (19, SD19; P<0.01), thereafter remaining at a plateau value of approximately 15 (P>0.05). Seroma incidence was reduced in the quilted group (5% vs 70%). A strong, significant correlation was found between 3 month DASH score and long term function (r=0.66, P<0.0003); patients with DASH >20 fare significantly worse in the longterm (mean 20 point increase, SD5.0, P<0.001). Higher post-operative DASH scores correlated significantly with pre-operative DASH (r=0.58) and BMI (r=0.36). Adjuvant therapy had no effect on shoulder function. Axillary dissection had a weak correlation with a higher DASH score, but only at the 3-month post-operative time-point (r=0.32, P=0.03). ALD flap breast reconstruction generally results in a functionally insignificant increase (6.5 points) in longterm DASH score, although a small subset of patients do develop longterm impairment, and quilting does not appear to inhibit shoulder function.

The nerve injury and the dying neurons : diagnosis and prevention

Following distal nerve injury significant sensory neuronal cell death occurs in the dorsal root ganglia, while after a more proximal injury, such as brachial plexus injury, a sizeable proportion of spinal motoneurons also undergo cell death. This phenomenon has been undervalued for a long time, but it has a significant role in the lack of functional recuperation, as neuronal cells cannot divide and be replaced, hence the resulting nerve regeneration is usually suboptimal. It is now accepted that this cell death is due to apoptosis, as indicated by analysis of specific genes involved in the apoptotic signalling cascade. Immediate nerve repair, either by direct suturing or nerve grafting, gives a degree of neuroprotection, but this approach does not fully prevent neuronal cell death and importantly it is not always possible. Our work has shown that pharmacological intervention using either acetyl-L-carnitine (ALCAR) or N-acetyl-cysteine (NAC) give complete neuroprotection in different types of peripheral nerve injury. Both compounds are clinically safe and experimental work has defined the best dose, timing after injury and duration of administration. The efficacy of neuroprotection of ALCAR and NAC can be monitored non-invasively using MRI, as demonstrated experimentally and more recently by clinical studies of the volume of dorsal root ganglia. Translation to patients of this pharmacological intervention requires further work, but the available results indicate that this approach will help to secure a better functional outcome following peripheral nerve injury and repair.

Topographic anatomy of the nerve to masseter: An anatomical and clinical study

BACKGROUND The use of the motor nerve to masseter has proved to be a reliable and sensible solution in facial reanimation as a donor for free muscle transfer. In this paper we describe the topographic anatomy of the nerve to masseter and our original technique for its quick and safe harvesting. METHODS This anatomical study is based on the dissection of the nerve to masseter in 17 embalmed cadaverous sites and is focused on the anatomical relations between the nerve and the surrounding structures. Also buccal and zygomatic branches of the facial nerve were dissected and assessed and the resulting data are compared. RESULTS The nerve to masseter has a predictable track inside the muscle which can be identified topographically within a square area under the zygomatic arch. This area is different between males and females and its accuracy has been tested on six patients at the Canniesburn Unit. CONCLUSIONS The nerve to masseter emerges in a very predictable point from the mandibular notch - immediately below the zygomatic arch - to run within the muscle belly. The approach here described allows safer and faster harvesting of the nerve to masseter with minimal dissection through the muscle.

Frozen-section fluorescence microscopy and stereology in the quantification of neuronal death within dorsal root ganglia.

Histochemical and morphological research increasingly relies upon quantification of complex biological systems. For such investigations to be meaningful, quantification techniques must meet the seemingly conflicting requirements of being theoretically robust, yet sufficiently practical to facilitate widespread applicability. Validity ought to be enhanced by theoretical simplicity, use of measured rather than assumed variables, and minimising observer interpretation. Practicality is facilitated by simplifying and reducing measurements, broadening applicability, and reducing costs and analysis time. As a result, quantification systems that rely upon sampling and estimation have been favoured over serial reconstruction techniques. To provide reliable estimates, sampling must be valid at all levels from tissue harvest, to the selection of microscope fields in which quantification is performed by techniques that account for the anisotropic distribution, and variable size of many elements in biological systems. These principles are embodied in the development of a stereological approach to the quantification of neuronal death within dorsal root ganglia after peripheral nerve injury. This frozen section technique is efficient and flexible, since it permits simultaneous morphological examination, TUNEL, or standard fluorescence immunohistochemistry, broadening its applicability. Section shrinkage is minimal, and counting by optical disection has proved to be time-efficient and sufficiently reproducible to reliably detect losses in the order of 5, with minimal inter-observer variation. As is discussed, stereology has not yet met with universal acceptance, but by balancing theoretical validity with practical applicability, it has proved an excellent approach to the investigation of neuronal death within dorsal root ganglia. Frozen-section fluorescence microscopy and stereology in the quantification of neuronal death within dorsal root ganglia

Use of Integra to resurface a latissimus dorsi free flap

The successful use of Integra to cover a muscle flap as a secondary reconstructive procedure is presented.

Surgical treatment of a Morel-Lavallee lesion of the distal thigh with the use of lymphatic mapping and fibrin sealant

INTRODUCTION A Morel-Lavallée lesion can occur after a closed degloving injury. It is a persistent seroma that may be resistant to conservative methods of treatment such as percutaneous drainage and compression therapy. We present a novel, successful method of surgical treatment. CASE REPORT A 70 year-old lady developed a 30 × 15 cm rapidly enlarging right medial thigh/knee swelling after being hit by a car. Conservative treatments failed, sarcoma was excluded, and the diagnosis confirmed, by MR imaging and cytology prior to referral. The lesion was excised, and blue dye lymphatic mapping used to identify and ligate feeding lymphatic vessels. The cavity was then closed using fibrin sealant spray and resorbable quilting sutures. A pressure garment was fitted. RESULT The wound healed without complication, with no recurrence at six months. The patient returned to normal activities without pressure garments. CONCLUSION This method provides a novel, successful approach to the surgical treatment of a chronic Morel-Lavallée lesion.

Tissue Engineering for Peripheral Nerve Regeneration

The outcome of peripheral nerve repair has changed very little over the past 50 years, and clinical outcomes remain generally poor. Surgical technique has evolved to a high level of technical microsurgical proficiency, but this approach remains unable to adequately address the neurobiological barriers to the optimization of nerve regeneration. Reconstruction of complex segmental injuries, as in the brachial plexus, additionally requires a considerable length of interpositional nerve autograft, which may be unobtainable without considerable donor morbidity.

The anatomic and radiologic basis of the circumflex scapular artery perforator flap

Microsurgical development has recently focused upon the perforator paradigm and primary thinning. Existing perforator flaps may require intramuscular dissection or lack reliable surface markings, whereas traditional scapular/parascapular flaps have low donor morbidity and reliable anatomy, but can be excessively bulky. Clinical application of a new flap based on a perforator from the circumflex scapular axis (CSA) has recently been published, but the vessels anatomy has not been adequately characterized. The CSA was dissected in 115 sites in 69 cadavers. The number, external vessel diameter, and site of origin of perforators were measured relative to the CSA bifurcation. Color Doppler ultrasound was used to delineate the CSA and its perforators bilaterally in 40 volunteers. The number, origin relative to CSA bifurcation, diameter, length, and flow velocity of cutaneous perforators were determined. A CSA perforator was always present, running into the subdermal plexus, arising within 2.4 cm of the bifurcation. Cadaver studies: mean perforator diameter, 1.3 mm (SD, 0.66); 13% arose at bifurcation, 36% arose proximal (mean, 1.1 mm; SD, 0.63), and 52% distal to bifurcation (mean, 1.5 mm; SD, 0.88). Ultrasound: mean perforator diameter, 1.18 mm (SD, 0.41); mean flow velocity, 16.3 cm/s (SD, 3.65); perforator arose in 36% proximal, in 40% distal to bifurcation, and in 24% from the bifurcation. We definitively describe the anatomy of the perforator from the circumflex scapular artery upon which a new flap has been based. Its origin and dimensions are anatomically and radiologically reliable. The flap has certain potential benefits over existing perforator flaps.