Sensory Deficiencies Research Articles

Comparing tests of tactile sensibility: aspects relevant to testing children with spastic hemiplegia

Children with hemiplegic cerebral palsy (CP) commonly exhibit tactile sensory deficiencies in their hands in addition to their motor problems. The aim of this study was to compare and evaluate the usefulness of some common tests of tactile sensibility for use with children with hemiplegic CP. Twenty‐five children with hemiplegia aged between 5 and 18 years, and 19 control individuals participated. All children were examined with Semmes‐Weinstein monofilaments, two‐point discrimination (2PD), stereognosis of familiar objects, stereognosis of forms, and functional sensibility. Dexterity, spasticity, and bimanual task performance were also assessed. Results from the different sensory tests deviated greatly. We found three tests to be useful: 2PD of 3mm spacing, which was the most sensitive test, stereognosis of familiar objects, and functional sensibility assessed through the Pick‐up test (comparing performance with and without the influence of vision). Stereognosis of forms and threshold values of touch (Semmes‐Weinstein monofilaments) are seemingly less useful tests for children with CNS impairments. Deficient sensibility was strongly related to dexterity. Aspects concerning the testing methodology are discussed.

Sensory Impairments and Delayed Regeneration of Sensory Axons in Interleukin-6-Deficient Mice

Interleukin-6 (IL-6) is a multifunctional cytokine mediating inflammatory or immune reactions. Here we investigated the possible role of IL-6 in the intact or lesioned peripheral nervous system using adult IL-6 gene knockout (IL-6(-/-)) mice. Various sensory functions were tested by applying electrophysiological, morphological, biochemical, and behavioral methods. There was a 60% reduction of the compound action potential of the sensory branch of IL-6(-/-) mice as compared with the motor branch in the intact sciatic nerve. Cross sections of L5 DRG of IL-6(-/-) mice showed a shift in the relative size distribution of the neurons. The temperature sensitivity of IL-6(-/-) mice was also significantly reduced. After crush lesion of the sciatic nerve, its functional recovery was delayed in IL-6(-/-) mice as analyzed from a behavioral footprint assay. Measurements of compound action potentials 20 d after crush lesion showed that there was a very low level of recovery of the sensory but not of the motor branch of IL-6(-/-) mice. Similar results of sensory impairments were obtained with mice showing slow Wallerian degeneration (Wlds) and a delayed lesion-induced recruitment of macrophages. However, in contrast to WldS mice, in IL-6(-/-) mice we observed the characteristic lesion-induced invasion of macrophages and the upregulation of low-affinity neurotrophin receptor p75 (p75LNTR) mRNA levels identical to those of IL-6(+/+) mice. Thus, the mechanisms leading to the common sensory deficiencies were different between IL-6(-/-) and WldS mice. Altogether, the results suggest that interleukin-6 is essential to modulate sensory functions in vivo.

Cyclist's palsy: Neurological and EMG study in 4 cases with distal ulnar lesions

Four cases of cyclist's palsy — a distal compression syndrome of the ulnar nerve which can develop after long cycling tours — are described. In two patients extensive neurological and electromyographic (EMG) studies were performed in order to document the degree and time course of recovery of the motor and sensory deficiencies. In contrast to earlier EMG-studies it could be demonstrated that not only the deep motor branch of the ulnar nerve is involved, but also that a severe lesion of the superficial branch supplying the skin of the 4th and 5th finger can occur, as indicated by a complete loss of the orthodromic sensory action potential recorded above the ulnar nerve in both cases. The results furthermore show that a functionally significant paresis of the hand muscles can persist for several months. The pathogenesis and some practical implications will be discussed.

The eyes and skin of Octopus: compensating for sensory deficiencies

Octopuses are the chameleons of the sea and can change their appearance to an extraordinary degree. Yet recent experiments, described here, show that they are almost certainly colour-blind. They blend in with their background primarily because of their neurally-controlled chromatophores, which, regulated by information from an eye sensitive to brightness, constitute a system for matching luminance. Deeper in the skin, however, there is a system of broad-band reflectors (the leucophores and iridophores). When the overlying chromatophores retract, these will automatically reflect incident light, whatever its wavelength.