Sensory reinnervation in microsurgical reconstruction of the heel

Six sensory reinnervation techniques were carried out in 10 patients who underwent reconstruction of the weight-bearing surface of the heel by microsurgical free-tissue transfer. The techniques include the use of neurovascular island flaps, neurosensory flaps, sensory nerve grafts to skin flaps, coaptation of the sensory nerve to the motor nerve of the muscle flaps, direct sensory nerve transfer, and sensory nerve graft transfer. In all patients, some sensation developed, characterized by sensation to light touch, to dull objects, to pinprick, to pain, and to tickling. Three patients developed the ability to distinguish sharp from dull objects and the sensation of pain. The remaining seven had the sensation of touch to various mechanical stimuli. In nine patients, the sensation is located in the weight-bearing surface of the reconstructed heel. Five patients bear weight on the reconstructed surface at least 6 hours per day. Three participate actively in sports. Split-thickness skin graft-muscle flaps were more prone to breakdown than skin flaps. Full-thickness skin flaps appear necessary for the production of pain sensation and the more discriminating sensations. Preliminary results suggest a functional benefit after sensory reinnervation.     

Competitive reinnervation of salamander skin by regenerating and intact mechanosensory nerves

We have investigated in the salamander the possibility that regenerating mechanosensory nerves might prefer the epidermal Merkel cells (their specific targets) that are located within their segmental domain to those within a "foreign" domain. Since regerating nerves cross domain boundaries with no evidence of the marked delay exhibited by intact sprouting nerves, we examined situations in which the regenerating axons of one segmental nerve were effectively in equal competition for denervated skin with those of another segmental nerve. Additionally, we investigated whether there were differences between regenerating axons and intact sprouting axons of the same segmental nerve, in their ability to innervate available skin both inside and outside the parent domain. No preference was detected of any type of nerve, regenerating or intact, for particular skin regions, or for Merkel cells as indicated by the numbers of mechanosensory thresholds of the touch spots that developed in reinnervated skin. Neither was there any indicating of displacement of "foreign" nerves from a particular region by appropriate axons. When regenerating and intact (sprouting) axons invaded denervated skin more or less simultaneously, the former appeared to have a slight advantage since a significantly greater proportion of skin was innervated by regenerated fibres. With this one exception, all the results were explained most simply by assuming that the axon that first arrives at a denervated Merkel cell establishes a permanent association with that cell and at the same time causes it to lose its "target character" for other axons.     

Comparing sensibility for touch,cold, and warmth in different skin areas

The primary objective of this pilot study was to assess if the magnitude estimation of suprathreshold brushing, warmth (40?°C), and cold (25?°C) stimuli of the skin over the dorsum of the hand and the dorsum of the foot are comparable to the perceived intensity for the same stimuli applied to the skin over any of the following areas: forehead, m. trapezius, m. deltoideus, thoracic back, and lumbar back, respectively. Thirty-two subjects aged 18–64 years were included. Participants were examined by two physicians on two different occasions, 1–58 days apart. Participants rated the magnitude of the perceived sensation of each stimulus on an 11-point numerical rating scale (NRS) 0–10, where 0 was anchored to “no sensation at all for touch/cold/warmth” and 10 anchored to “the most intense imaginable non-painful sensation of touch/cold/warmth”. The criterion for sensory equivalence for one modality was arbitrarily considered satisfactory if two regions had the same numerical rating ±1 point in at least 85% of the individuals. Based on the pre-study criteria for sensory equivalence applied in this study only one area was found to be equivalent to the foot skin for the percept of brushing, that is, the skin over the deltoid muscle and one area for the hand, that is, the skin over the forehead. We failed to find any area with equivalent sensitivity to the hand or the foot for the cold or warm stimuli.     

Sensory cells in the head skin of pond snails

Summary Several types of receptor endings were identified with scanning electron microscopy and silver-impregnation techniques in the skin of the tentacles, lips, dorsal surface of the head and mouth region of the pond snails Lymnaea stagnalis and Vivipara viviparus. Sensory endings at the tips of dendrites of primary receptor neurones, scattered below the epithelium, differ in structure, i.e., the endings exposed to the surface of the skin possess different proportions of cilia and microvilli, which vary in number, length, and packing. Type-I endings have microvilli and a few (1–5) cilia, 5–12 m in length. Type-2 endings have abundant (20–40), interwoven long (9–12 m) cilia and random microvilli. Type-3 endings show typical packing of 10–25 cilia in the form of bundles or brushes. They may be composed either of long (9–18 m) or short (2–7 m) cilia, or of both long and short ones. Microvilli here are absent. Type-4 endings have only microvilli. Two other types of skin receptors do not extend their sensory endings to the surface and can be indentified only in silver-stained preparations. Type-5 endings are branching dendrites of skin receptors cells that terminate among epithelial cells. In type-6, the sensory endings also terminate among epithelial cells but their cell bodies are located outside of the skin. In both species all skin regions examined possess the receptors of all six types differing only in their relative proportion. Possible functional roles of different receptors are discussed.     

Sensory and autonomic innervation of non-hairy and hairy human skin

Summary Non-hairy and hairy human skin were investigated with the use of the indirect immunohistochemical technique employing antisera to different neuronal and non-neuronal structural proteins and neurotransmitter candidates. Fibers immunoreactive to antisera against neurofilaments, neuron-specific enolase, myelin basic protein, protein S-100, substance P, neurokinin A, neuropeptide Y, tyrosine hydroxylase and vasoactive intestinal polypeptide (VIP) were detected in the skin with specific distributional patterns. Neurofilament-, neuron-specific enolase-, myelin basic protein-, protein S-100-, substance P-, neurokinin A-and vasoactive intestinal polypeptide (VIP)-like immunoreactivities were found in or in association with sensory nerves; moreover, neuron-specific enolase-, myelin basic protein-, protein S-100, neuropeptide Y-, tyrosine hydroxylase- and vasoactive intestinal polypeptide (VIP)-like immunoreactivities occurred in or in association with autonomic nerves. It was concluded that antiserum against neurofilaments labels sensory nerve fibers exclusively, whereas neuron-specific enolase-, myelin basic protein- and protein S-100-like immunoreactivities are found in or in association with both sensory and autonomic nerves. Substance P- and neurokinin A-like immunoreactivities were observed only in sensory nerve fibers, and neuropeptide Y- and tyrosine hydroxylase-like immunoreactivities occurred only in autonomic nerve fibers, whereas vasoactive intestinal polypeptide (VIP)-like immunoreactivity was seen predominantly in autonomic nerves, but also in some sensory nerve fibers.     

Reduction mammaplasty: a prospective study of symptom relief and alterations of skin sensibility

The aim of the present study was to evaluate the alterations of symptoms and tactile sensibility of the breast after reduction mammaplasty. In a prospective study, 10 women were operated on using the inferior pedicle technique. The patients were examined and interviewed preoperatively and at 2 weeks and 3 and 12 months postoperatively. Tactile sensibility was assessed by Somedic monofilaments applied on nine points on each breast: the nipple, four points on the areola, and in four quadrants of the skin. Preoperative tactile sensibility was compared with tactile sensibility in 10 normal controls. A median of 744 g of tissue was removed. All patients reported relief of shoulder and neck discomfort and improvement of skin sensibility 1 year after the operation. Two weeks after the operation, the sensibility of the areola was reduced (p < 0.05), but the skin sensibility of two quadrants was improved (p < 0.05). The sensibility of the areola was restored to preoperative values during the observation period. At 12 months, sensibility was improved compared with preoperative values both in the upper part of the areola and in three quadrants of the skin (p < 0.05). Significant improvement of skin sensibility was found between 3 and 12 months postoperatively in two quadrants of the breast. Also, the erectile function of the nipple was not altered by the operation. In conclusion, the sensibility of the breast was improved or unchanged 1 year after reduction mammaplasty using the Robbins technique. Continuous improvement of sensibility was found during the 1-year observation period. The evidence provided by this prospective study rules out the common misconception that a reduction mammaplasty gives the patient reduced areola sensibility and altered erectile function.     

Sensory neuroscience: from skin to object in the somatosensory cortex

Humans can perceive the shape of objects by touch alone, by extracting geometric features such as edges. Recently recorded responses of single neurons in the secondary somatosensory cortex of monkeys suggest how the brain integrates tactile shape information across different regions of skin and builds up a representation of tactile objects.