High densities of opioid receptors are located in all areas of the central nervous system known to be involved in integrating information about pain such as cingulate cortex, periaqueductal
gray matter and reticular formation (8) and, these major structures of the medial pain system have a very high concentration of opioid receptors (5).
Leigh syndrome is diagnosed on the basis of progressive neurologic regression, often provoked by an infection, along with characteristic MRI findings (T2 prolongation in bilateral basal ganglia, in particular the putamen, brainstem nuclei, periaqueductal
gray matter, and central white matter).
A Papadopoulou et al (Basel, Switzerland) reported that the use of 30 double invention recovery (DIR) sequence was of particular value as it allows identification of periaqueductal
lesions in MS patients.
They abut each other at the midline immediately anterior (ventral) to the periaqueductal
grey (PAG) surrounding the cerebral aqueduct and posterior (dorsal) to the medial longitudinal fasciculus (MLF) carrying connections between various brainstem nuclei involved in ocular motor control (Figure 3).
Abnormal histiogenesis and proliferation of periaqueductal
grey matter in the midbrain can result in primary stenosis or formation of numerous minute channels through the aqueduct.
Interictal alterations of the trigeminal somatosensory pathway and periaqueductal
gray matter in migraine.
These receptors are found in various central nervous system areas that are involved in pain perception and modulation, such as the periaqueductal
grey, the thalamus, and the spinal cord dorsal horn .
Fibers containing endorphin project from the arcuate nucleus to other hypothalamic nuclei as well as to the septum, NAc, periaqueductal
gray area, amygdala, and hippocampus.
Western medicine hypothesises that signals from stimulation of peripheral nerve fibres (possibly through acupuncture points) can influence hypothalamic functions via the dorsal periaqueductal
grey fibres, and thereby influence the respiratory centre in the medulla, modifying respiration (Takeshige et al 1993).
There is often involvement of surrounding periventricular and periaqueductal
tissue such as dorsal pons, midbrain, thalamus, or pineal region, and multinodularity or multicentricity may be observed.
2] receptors of the periaqueductal
gray and inferior colliculus induces fear-like behaviors.
Associated neurobiological structures and functions associated with the FFFS are the periaqueductal
grey, medial hypothalamus, and amygdala, and serotonergic inputs into these structures.