Pain activation of human supraspinal opioid pathways as demonstrated by [11C]-carfentanil and positron emission tomography (PET).

The role of the supraspinal endogenous opioid system in pain processing has been investigated in this study using positron emission tomography imaging of [11C]-carfentanil, a synthetic, highly specific mu opioid receptor (mu-OR) agonist. Eight healthy volunteers were studied during a baseline imaging session and during a session in which subjects experienced pain induced by applying capsaicin topically to the dorsal aspect of the left hand. A pain-related decrease in brain mu-OR binding was observed in the contralateral thalamus consistent with competitive binding between [11C]-carfentanil and acutely released endogenous opioid peptides. This decrease varied directly with ratings of pain intensity. These results suggest that the supraspinal mu-opioid system is activated by acute pain and thus may play a substantial role in pain processing and modulation in pain syndromes.

Intracranial extension of an idiopathic orbital inflammatory pseudotumor.

Idiopathic orbital inflammatory pseudotumor (IOIP) with endocranial extension is very unusual. The authors used CT and MR to diagnose IOIP and demonstrate the presence of intracranial extension of orbital and lacrimal gland lesions. While providing additional evidence of IOIP having intracranial extension, this case report emphasizes the need to include IOIP as a possible differential diagnosis when radiologic explorations reveal lesions extending from the orbit to intracranial structures.

Imaging in the exploration of lumbosacral plexus avulsion. Two cases.

In all cases of post-traumatic sensorimotor deficit in the lower limbs unexplained by another pathology, it is not unreasonable to suspect a nerve root avulsion. Whenever available, MRI seems to be the choice examination as it is not invasive and provides a three-dimensional exploration. On the basis of two new cases and a review of the literature, the authors discuss the value of various imaging methods in this pathology.

Choroid plexus papillomas of the posterior fossa in adults: MR imaging and gadolinium enhancement. Report of four cases and review of the literature.

Four cases of benign choroid plexus papillomas of the posterior fossa in adults are reported: two papillomas developed in the fourth ventricle, one in the cerebellopontine angle, and one extended from the fourth ventricle to the cerebellopontine angle. CT, MRI and surgical findings are described. The MRI characteristics on T1 and T2-weighted sequences are compared with those already published. In three cases the tumour signal observed after gadolinium enhancement was intense and homogeneous. The paramagnetic contrast agent provided direct visualization and better discrimination of papilloma location and extent.

PET imaging of brain acetylcholinesterase using [11C]CP-126,998, a brain selective enzyme inhibitor.

PET and [(11)C]CP-126,998, an N-benzylpiperidinebenzisoxazole, were used to image brain acetylcholinesterase (AChE) distribution in healthy controls before and after administration of 5 mg donepezil p.o., a reversible AChE inhibitor. Logan plots were used to compute distribution volumes (V(T)). The V(T) of [(11)C]CP-126,998 was highest in the basal ganglia and cerebellum and lowest in the cerebral cortex, thalamus, amygdala, and hippocampus. The regional V(T) values correlated well with AChE concentration measured in vitro. Donepezil, given 4 h before PET scanning, induced a substantial inhibition of [(11)C]CP-126,998 binding (43-62%) in all brain regions when compared to the baseline PET study. The results of this study indicate that PET imaging of [(11)C]CP-126,998 may be useful in quantifying the distribution of regional brain AChE. This new PET radiotracer may potentially be employed in the diagnosis and treatment of patients with disorders of cholinergic neurotransmission, such as Alzheimer's disease.