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.

Expression of adenosine A2a receptors gene in the olfactory bulb and spinal cord of rat and mouse

The expression of adenosine A2a receptors (A2aR) in the mammalian striatum is well known. In contrast the exact distribution of A2aR in other regions of the central nervous system remains unclear. The aim of this study was to investigate the A2aR gene expression in the rat olfactory bulb and spinal cord, two regions which are seldom included in mapping studies. Secondly, we compared the A2aR expression in the rat and in the mouse brain. Hybridization histochemistry was performed with an S35-labelled radioactive oligonucleotide probe. The results show strong expression of A2aR in the mouse and rat striatum in accordance with previous reports. In the olfactory bulb a weak but specific expression of A2aR was found in the granular cell layer in both species. In contrast, no significant expression of the A2aR gene was observed in other parts of the brain or the rat spinal cord. The presence of the A2aR in the mammalian olfactory bulb suggests a functional role for this receptor in olfaction.

Ultrasound-guided needle positioning in sensory nerve conduction study of the sural nerve

OBJECTIVES: To evaluate the usefulness of ultrasound imaging to improve the positioning of the recording needle for nerve conduction studies (NCS) of the sural nerve. METHODS: Orthodromic NCS of the sural nerve was performed in 44 consecutive patients evaluated for polyneuropathy. Ultrasound-guided needle positioning (USNP) was compared to conventional "blind" needle positioning (BNP), electrically guided needle positioning (EGNP), and to recordings with surface electrodes (SFN). RESULTS: The mean distance between the needle tip and the nerve was 1.1 mm with USNP compared to 5.1 mm with BNP (p<0.0001). The mean amplitude of the sensory nerve action potential (SNAP) was 21 microV with USNP and 11 microV with BNP (p<0.0001). Compared to BNP, nerve-needle distances and SNAP amplitudes did not improve with EGNP. SNAP amplitudes recorded with SFN were significantly smaller than with BNP, EGNP and USNP. CONCLUSION: Ultrasound increases the precision of needle positioning markedly, compared to conventional methods. The amplitude of the recorded SNAP is usually clearly greater using USNP. In addition, USNP is faster, less painful and less dependent on the patient. SIGNIFICANCE: USNP is superior to BNP, EGNP, and SFN in accurate measurement of SNAP amplitude. It has a potential use in the routine near-nerve needle sensory NCS of pure sensory nerves.

Capsular warning syndrome mimicking a jacksonian sensory march

A 57-year-old man, operated eight years before for a left frontal falx meningioma, presented with short lasting, stereotyped episodes of paresthesias ascending from the right foot to the hand. A diagnosis of somatosensory seizures with jacksonian march was made. The patient was given antiepilectics but 5 days later, a few hours after another paresthesic episodes, he developed right hemiplegia, hemianesthesia and dysartria due to an infarct of left capsular posterior limb. We deem that in this patient the paresthesic episodes were more likely an expression of a capsular warning syndrome than of parietal epilepsy because of the frontal localization of the surgical lesion, the absence of motor components in all episodes, the negativity of repeated EEG, and the lack of recurrences after stroke. In capsular warning syndrome sensory symptoms mimicking a jacksonian march can be due to ischemic depolarization progressively recruiting the somatotopically arranged sensory fibers in the posterior capsular limb.

Assortative mating among Lake Malawi cichlid fish populations is not simply predictable from male nuptial colour

Background: Research on the evolution of reproductive isolation in African cichlid fishes has largely focussed on the role of male colours and female mate choice. Here, we tested predictions from the hypothesis that allopatric divergence in male colour is associated with corresponding divergence in preference. Methods: We studied four populations of the Lake Malawi Pseudotropheus zebra complex. We predicted that more distantly-related populations that independently evolved similar colours would interbreed freely while more closely-related populations with different colours mate assortatively. We used microsatellite genotypes or mesh false-floors to assign paternity. Fisher's exact tests as well as Binomial and Wilcoxon tests were used to detect if mating departed from random expectations. Results: Surprisingly, laboratory mate choice experiments revealed significant assortative mating not only between population pairs with differently coloured males, but between population pairs with similarly-coloured males too. This suggested that assortative mating could be based on nonvisual cues, so we further examined the sensory basis of assortative mating between two populations with different male colour. Conducting trials under monochromatic (orange) light, intended to mask the distinctive male dorsal fin hues (blue v orange) of these populations, did not significantly affect the assortative mating by female P. emmiltos observed under control conditions. By contrast, assortative mating broke down when direct contact between female and male was prevented. Conclusion: We suggest that non-visual cues, such as olfactory signals, may play an important role in mate choice and behavioural isolation in these and perhaps other African cichlid fish. Future speciation models aimed at explaining African cichlid radiations may therefore consider incorporating such mating cues in mate choice scenarios.

Non-selective cutaneous sensory neurectomy as an alternative treatment for auto-mutilation lesion following arthrodesis in three dogs

OBJECTIVE: To describe an alternative method for the treatment of non-responsive self-mutilation injuries in three dogs after carpal/tarsal arthrodesis. STUDY DESIGN: Case series ANIMALS: Two dogs with carpal injury and one dog with tarsal injury treated by arthrodesis METHODS: All dogs developed self-mutilation injuries due to licking and/or chewing of the toes within 21-52 days of surgery. Clinical signs did not resolve within one week after conservative treatment with wound debridement and protective bandages. Following general anaesthesia, a deep horseshoe-shaped skin incision, including the subdermal tissue, was performed proximal to the self-mutilation injury transecting the sensory cutaneous afferent nerves. The skin incision was closed with simple interrupted sutures. RESULTS: All wounds healed without complication. Self-mutilation resolved completely within 24 hours after surgery in all dogs. No recurrence was observed (5 months to 3 years). CONCLUSION: Non-selective cutaneous sensory neurectomy may lead to resolution of self-mutilation following arthrodesis in dogs. CLINICAL RELEVANCE: Failure of conservative treatment in self-mutilation injuries often leads to toe or limb amputation as a last resort. The technique described in this case series is a simple procedure that should be considered prior to amputation. The outcome of this procedure in dogs self-multilating due to neurological or behavioral disturbances unrelated to carpal or tarsal arthrodesis is not known.

Beyond words: Sensory properties of depressive thoughts

Verbal thoughts (such as negative cognitions) and sensory phenomena (such as visual mental imagery) are usually conceptualised as distinct mental experiences. The present study examined to what extent depressive thoughts are accompanied by sensory experiences and how this is associated with symptom severity, insight of illness and quality of life. A large sample of mildly to moderately depressed patients (N = 356) was recruited from multiple sources and asked about sensory properties of their depressive thoughts in an online study. Diagnostic status and symptom severity were established over a telephone interview with trained raters. Sensory properties of negative thoughts were reported by 56.5% of the sample (i.e., sensation in at least one sensory modality). The highest prevalence was seen for bodily (39.6%) followed by auditory (30.6%) and visual (27.2%) sensations. Patients reporting sensory properties of thoughts showed more severe psychopathological symptoms than those who did not. The degree of perceptuality was marginally associated with quality of life. The findings support the notion that depressive thoughts are not only verbal but commonly accompanied by sensory experiences. The perceptuality of depressive thoughts and the resulting sense of authenticity may contribute to the emotional impact and pervasiveness of such thoughts, making them difficult to dismiss for their holder.

Perceptual and processing differences between physical and dichorhinic odor mixtures

Perceptual integration of sensory input from our two nostrils has received little attention in comparison to lateralized inputs for vision and hearing. Here, we investigated whether a binary odor mixture of eugenol and l-carvone (smells of cloves and caraway) would be perceived differently if presented as a mixture in one nostril (physical mixture), vs. the same two odorants in separate nostrils (dichorhinic mixture). In parallel, we investigated whether the different types of presentation resulted in differences in olfactory event-related potentials (OERP). Psychophysical ratings showed that the dichorhinic mixtures were perceived as more intense than the physical mixtures. A tendency for shift in perceived quality was also observed. In line with these perceptual changes, the OERP showed a shift in latencies and amplitudes for early (more "sensory") peaks P1 and N1 whereas no significant differences were observed for the later (more "cognitive") peak P2. The results altogether suggest that the peripheral level is a site of interaction between odorants. Both psychophysical ratings and, for the first time, electrophysiological measurements converge on this conclusion.

Reduced olfactory bulb volume in adults with a history of childhood maltreatment

The human olfactory bulb (OB) is the first relay station of the olfactory pathway and may have the potential for postnatal neurogenesis in early childhood. In animals, chronic stress affects the OB and olfactory functioning. For humans, it has been shown that major depressive disorder is accompanied by reduced OB volume and reduced olfactory function. However, it is not clear if major stress in childhood development also affects olfactory functioning and OB volume in humans. OB volume was measured and olfactory function was tested in 17 depressive patients with and 10 without a history of severe childhood maltreatment (CM). CM patients exhibited a significantly reduced olfactory threshold and identification ability. The OB volume of the CM patients was significantly reduced to 80% of the non-CM patients. In conclusion, postnatal neurogenesis might be by reduced in CM, which may affect olfactory function of the brain in later life. Alternatively, a reduced OB volume may enhance psychological vulnerability in the presence of adverse childhood conditions although other areas not analyzed in this study may also be involved.