Fibromyalgia syndrome is a clinically well-characterized chronic pain condition of high socio-economic impact. Although the pathophysiology is still unclear, there is increasing evidence for nervous system dysfunction in patients with fibromyalgia syndrome. In this case-control study we investigated function and morphology of small nerve fibres in 25 patients with fibromyalgia syndrome. Patients underwent comprehensive neurological and neurophysiological assessment. We examined small fibre function by quantitative sensory testing and pain-related evoked potentials, and quantified intraepidermal nerve fibre density and regenerating intraepidermal nerve fibres in skin punch biopsies of the lower leg and upper thigh. The results were compared with data from 10 patients with monopolar depression without pain and with healthy control subjects matched for age and gender. Neurological and standard neurophysiological examination was normal in all patients, excluding large fibre polyneuropathy. Patients with fibromyalgia syndrome had increased scores in neuropathic pain questionnaires compared with patients with depression and with control subjects (P < 0.001 each). Compared with control subjects, patients with fibromyalgia syndrome but not patients with depression had impaired small fibre function with increased cold and warm detection thresholds in quantitative sensory testing (P < 0.001). Investigation of pain-related evoked potentials revealed increased N1 latencies upon stimulation at the feet (P < 0.001) and reduced amplitudes of pain-related evoked potentials upon stimulation of face, hands and feet (P < 0.001) in patients with fibromyalgia syndrome compared to patients with depression and to control subjects, indicating abnormalities of small fibres or their central afferents. In skin biopsies total (P < 0.001) and regenerating intraepidermal nerve fibres (P < 0.01) at the lower leg and upper thigh were reduced in patients with fibromyalgia syndrome compared with control subjects. Accordingly, a reduction in dermal unmyelinated nerve fibre bundles was found in skin samples of patients with fibromyalgia syndrome compared with patients with depression and with healthy control subjects, whereas myelinated nerve fibres were spared. All three methods used support the concept of impaired small fibre function in patients with fibromyalgia syndrome, pointing towards a neuropathic nature of pain in fibromyalgia syndrome.

To detect morphologic abnormalities in Parkinson's disease (PD), we examined 30 patients with PD and 30 age- and sex-matched nonparkinsonian controls by transcranial color-coded real-time sonography (TCCS). In 12 severely affected PD patients, the echogenicity of the substantia nigra was distinctly increased. In the remaining 18 PD patients and in all controls, the substantia nigra was poorly visualized or nondetectable by TCCS. The degree of hyperechogenicity of the substantia nigra closely correlated with the severity and duration of PD (p < 0.001). The increased echogenicity of the substantia nigra notably results from nigral gliosis and reflects the stage of degeneration.

CURRENT treatment of Parkinson disease (PD) is basically symptomatic. So far, no neuroprotective strategy has proved to be effective in the clinical setting, although concepts and results of animal experiments have been promising.¹ One important reason for the failure of neuroprotection may be the fact that nigrostriatal degeneration has advanced to a 60% to 70% reduction of neurons in the substantia nigra (SN) at the time when the first clinical symptoms of PD are noticed by the patient.² It is possible that at this stage of the disease, drugs with a potential neuroprotective effect are no longer capable of arresting or slowing the course of degeneration. However, the speed of neurodegeneration might be reduced by the commencement of neuroprotective treatment in an earlier (preclinical) stage of PD.

Objective: To assess the incidence of a hyperechogenic substantia nigra (SN) by transcranial sonography (TCS) in healthy people and to evaluate whether an enlarged hyperechogenic SN area is associated with functional impairment of the nigrostriatal system. Background and Methods: Until now, preclinical impairment of the nigrostriatal system could be identified only by functional neuroimaging techniques such as PET in selected groups of patients. TCS is a new, noninvasive ultrasound technique that has demonstrated an increased echogenicity of the SN in patients with PD, whereas in most healthy individuals, the SN is either barely detectable or undetectable by TCS. Results: Of 330 healthy volunteers, 8.6% exhibited an increased echogenicity of the SN. From these, 10 clinically healthy individuals with distinct unilateral or bilateral hyperechogenic signals in the SN region (SN area above 0.25 cm²) underwent comprehensive motor testing, neuropsychological assessment, MRI, and [¹⁸F]-dopa PET examination. With regard to motor functions, these individuals did not differ from 10 age- and sex-matched controls with a low echogenic SN and an area of echogenic signals below 0.2 cm². Enlargement of hyperechogenic areas in the 10 healthy individuals was associated with a marked decrease in the accumulation of [¹⁸F]-dopa in the caudate nucleus and putamen. Conclusions: Substantia nigra hyperechogenicity appears to indicate a functional impairment of the nigrostriatal system. Transcranial sonography may be a suitable method of identifying persons at risk of nigrostriatal alterations, making possible the introduction of early neuroprotective therapy.

A novel Hebbian stimulation paradigm was employed to examine physiological correlates of motor memory formation in humans. Repetitive pairing of median nerve stimulation with transcranial magnetic stimulation over the contralateral motor cortex (paired associative stimulation, PAS) may decrease human motor cortical excitability at interstimulus intervals of 10 ms (PAS10) or increase excitability at 25 ms (PAS25). The properties of this plasticity have previously been shown to resemble associative timing-dependent long-term depression (LTD) and long-term potentiation (LTP) as established in vitro. Immediately after training a novel dynamic motor task, the capacity of the motor cortex to undergo plasticity in response to PAS25 was abolished. PAS10-induced plasticity remained unchanged. When retested after 6 h, PAS25-induced plasticity recovered to baseline levels. After training, normal PAS25-induced plasticity was observed in the contralateral training-naive motor cortex. Motor training did not reduce the efficacy of PAS25 to enhance cortical excitability when PAS10 was interspersed between the training and application of the PAS25 protocol. This indicated that the mechanism supporting PAS25-induced plasticity had remained intact immediately after training. Behavioral evidence was obtained for continued optimization of force generation at a time when PAS25-induced plasticity was blocked in the training motor cortex. Application of the PAS protocols after motor training did not prevent the consolidation of motor skills evident as performance gains at later retesting. The results are consistent with a concept of temporary suppression of associative cortical plasticity by neuronal mechanisms involved in motor training. Although it remains an open question exactly which element of motor training was responsible for this effect, our findings may link dynamic properties of LTP formation, as established in animal experiments, with human motor memory formation and possibly dynamic motor learning.