Magnetic resonance imaging in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a tauopathy, presenting clinically most often with a symmetrical akinetic-rigid syndrome, postural instability, supranuclear gaze palsy and frontal dementia. In the absence of reliably validated biomarkers, the diagnosis of PSP in vivo is presently based on clinical criteria, which to date do not include supporting imaging findings, as is accepted for other neurodegenerative diseases. However, data from conventional magnetic resonance imaging (MRI) and various advanced MRI techniques including magnetic resonance volumetry, voxel-based morphometry, diffusion-weighted and diffusion-tensor imaging, magnetization transfer imaging and proton resonance spectroscopy suggest that MRI can contribute valuable information for the differential diagnosis of PSP. We review here the presently published literature concerning MRI in PSP and discuss the potential role of MRI in differentiating PSP from other parkinsonian syndromes.

Men and women are different: diffusion tensor imaging reveals sexual dimorphism in the microstructure of the thalamus, corpus callosum and cingulum

INTRODUCTION

Numerous magnetic resonance imaging (MRI) studies have addressed the question of morphological differences of the brain of men and women, reporting conflicting results regarding brain size and the ratio of gray and white matter. In the present study, we used diffusion tensor imaging (DTI) to delineate sex differences of brain white matter.

METHODS

We investigated brain microstructure in 25 male and 25 female healthy subjects using a 3T MRI scanner. Whole-head DTI scans were analyzed without a-priori hypothesis using Tract-Based Spatial Statistics (TBSS) calculating maps of fractional anisotropy (FA), radial diffusivity (RD, a potential marker of glial alteration and changes in myelination) and axial diffusivity (AD, a potential marker of axonal changes).

RESULTS

DTI revealed regional microstructural differences between the brains of male and female subjects. Those were prominent in the thalamus, corpus callosum and cingulum. Men showed significantly (p<0.0001) higher values of fractional anisotropy and lower radial diffusivity in these areas, suggesting that the observed differences are mainly due to differences in myelination.

DISCUSSION

As a novel finding we showed widespread differences in thalamic microstructure that have not been described previously. Additionally, the present study confirmed earlier DTI studies focusing on sexual dimorphism in the corpus callosum and cingulum. All changes appear to be based on differences in myelination. The sex differences in thalamic microstructure call for further studies on the underlying cause and the behavioral correlates of this sexual dimorphism. Future DTI group studies may carefully control for gender to avoid confounding.

[The relationship between psychiatry and neurology]

Neurology and psychiatry deal with diseases of the (central) nervous system. Historically neurological disorders are related to a proven organic basis, whereas psychiatric disorders are mainly defined by the phenomenology and course of the symptoms. Neuroscientific research methods such as molecular genetics, neurochemistry, neurophysiology, neuropathology, functional (SPECT, PET, fMRI) or structural (MRI) imaging have dramatically increased our knowledge of psychiatric and neurological disorders in the last 20 years. Accordingly diagnostic and therapeutic procedures and the long-term prognosis of numerous diseases in both disciplines have substantially improved (i.e. pharmacotherapy, psychotherapy, functional neurosurgery). For major brain disorders - such as dementia of the Alzheimer type - close collaboration between both disciplines is developing in diagnosis, therapy and care. Due to common neurobiological research topics, educational programs, medical training and the challenges of assuring appropriate care to patients with brain disorders, further cooperation between neurology and psychiatry is expected and necessary.

Parasympathetic but not sympathetic cardiac dysfunction at early stages of Parkinson's disease

BACKGROUND

Autonomic cardiovascular dysfunction is common in Parkinson's disease (PD). Imaging studies suggest loss of cardiac sympathetic nerves even in the absence of clinical signs of autonomic dysfunction. Aim of the study was to investigate the functional significance of autonomic cardiovascular denervation at early stages of PD.

METHODS

Seven PD patients (Hoehn and Yahr class 1 or 1.5) without clinical signs of autonomic dysfunction and seven age-matched healthy control subjects were studied. To evaluate the pre- and post-synaptic components of sympathetic innervation, dose-response curves of isoproterenol (no neuronal uptake) and epinephrine (neuronal uptake) on heart rate, contractility, cardiac output and systemic vascular resistance were determined echocardiographically. Additionally, measurements of baroreflex sensitivity and 24-h heart rate variability were done.

RESULTS

The chronotropic and inotropic responses during stimulation with isoproterenol and epinephrine were similar in PD patients and control subjects. Assessment of baroreflex sensitivity yielded no difference. Of the parameters of 24-h heart rate variability, only measures of high-frequency heart rate variation that more purely reflect parasympathetic activity were significantly depressed in PD patients as compared with control subjects.

CONCLUSIONS

The results of our study using direct determination of catecholamine-mediated chronotropic and contractile responses provide evidence against a functionally relevant sympathetic dysfunction. Possibly, sympathetic denervation is incomplete and the remaining fibers are sufficient for the maintenance of autonomic control. In contrast, the depression of several parameters of heart rate variability supports a significant change of parasympathetic activity at an early stage of PD with subclinical autonomic failure.

[Differential diagnosis of Parkinson's disease: current consensus criteria and outlook]

Parkinsonian-syndrome, clinically based on the combination of cardinal symptoms, could be the clinical manifestation of different, neuropathological defined entities. Because of the different prognostic, therapeutical and scientific implications a reliable differential diagnostic of the entities in early course of disease is desirable. For this purpose standardized clinical diagnostic criteria with sufficient validation against the gold standard of the neuropathological diagnostic are important. In this article, the clinical diagnostic criteria of atypical Parkinsonian-syndrome and their validity were discussed.

Low-frequency rTMS of the vertex in the prophylactic treatment of migraine

High-frequency repetitive transcranial magnetic stimulation (rTMS) increases and low-frequency rTMS decreases neural excitability. Clinically, rTMS shows beneficial effects in the treatment of neurological and psychiatric disorders. Furthermore, chronic and neuropathic pain has been shown to respond to rTMS treatment. A small pilot study revealed prophylactic effects of high-frequency rTMS in migraine. As there is evidence of neuronal hyperexcitability in migraine, we conducted a placebo-controlled, blinded study to evaluate the therapeutic effects of low-frequency rTMS in migraine. The primary end-point was defined as a reduction of migraine attacks compared with placebo, secondary outcomes were a reduction in the total number of days with headache, hours with headache, pain intensity and a decrease of analgesic intake for migraine. Twenty-seven migraineurs completed the study and were treated with rTMS on five consecutive days. For the verum group, two trains of 500 pulses with a frequency of 1 Hz were applied over vertex with a round coil. For the treatment of the placebo group, a figure-of-eight sham coil was used. A significant decrease of migraine attacks could be observed in the verum group. However, when comparing these effects with placebo, no significance was evident. The same was true concerning secondary outcome measures with regard to days with migraine and total hours with migraine. No effects were evident for pain intensity and use of analgesics. The rTMS treatment was tolerated well. rTMS stimulation over vertex with 1 Hz was not effective in migraine prophylaxis when compared with placebo. The positive effects regarding migraine attacks, days and total hours with migraine in the verum group are encouraging and indicate that further research on this topic is warranted.

Pain sensitivity and descending inhibition of pain in Parkinson's disease

BACKGROUND

Patients suffering from Parkinson's disease (PD) often complain about painful sensations. Recent studies detected increased subjective pain sensitivity and increased spinal nociception, which appeared to be reversible by dopaminergic treatment. Possibly, reduced descending pain inhibition contributes to this finding.

OBJECTIVE

Subjective pain thresholds as well as nociceptive reflex thresholds were investigated to isolate potential loci of the pathophysiological changes within the pain pathway. In addition, the diffuse noxious inhibitory control (DNIC) system as one form of descending control was assessed.

METHOD

15 patients with PD and 18 controls participated in the study. Electrical and heat pain thresholds as well as the nociceptive flexion reflex (NFR) thresholds were determined. Thereafter, the electrical pain thresholds were measured once during painful heat stimulation (conditioning stimulation) and twice during innocuous stimulation (control stimulation).

RESULTS

Patients with PD exhibited lower electrical and heat pain thresholds as well as lower NFR thresholds. Suppression of the electrical pain thresholds during painful heat stimulation (conditioning stimulation) compared with control stimulation did not differ significantly between the groups. No differences in the thresholds between patients with PD with and without clinical pain were seen.

CONCLUSIONS

Finding the NFR threshold to be decreased in addition to the decreased electrical and heat pain thresholds indicates that the pathophysiological changes either already reside at or reach down to the spinal level. Reduced activation of the DNIC system was apparently not associated with increased pain sensitivity, suggesting that DNIC-like mechanisms do not significantly contribute to clinical pain in PD.