Spinal adjusting produced increased separation (gapping) of the Z joints. Side-posture positioning also produced gapping, but less than that seen with lumbar side-posture adjusting. This study helps to increase understanding about the mechanism of action for spinal manipulation.

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The human trigeminal system mediates facial pain and somatosensory processing. The anatomic location of neuronal substrates and axonal pathways of the trigeminal system have previously been characterized with conventional in vitro methods. The present investigation implemented diffusion tensor imaging (DTI) and probabilistic tractography to first segment the peripheral trigeminal circuitry, trigeminal nerve branches (ophthalmic, maxillary, and mandibular nerves), ganglion, and nerve root. Subsequent segmentations involved the spinal trigeminal and trigeminal thalamic tracts, which respectively convey information to the spinal trigeminal nuclei and ventral thalamic regions. This latter procedure also identified 1) spinal thalamic ( (Fig. 1). The peripheral components are made up of both motor and sensory branches. Motor branches are found in the mandibular nerve and originate in the motor nucleus of the STN. Sensory information, including touch and position, is conveyed by sensory afferents to the principal sensory nucleus (Pr5), while pain and temperature fibers terminate in the trigeminal nuclei, caudalis, interpolaris, and oralis. The TNR enters the brainstem at the mid-pons and travels in rostral and caudal directions to various STN components. The central projections for pain and temperature sensations from the STN send afferents in the dorsal TTh (dTTh) that joins the spinal thalamic (STh) tract (anterolateral [AL] system) (Fig. 1). Similarly, the trigeminal lemniscus (TL; also referred to as the ventral TTh) and medial lemniscus (ML) convey both touch and position information from the face and body, respectively. These parallel tracts run in very close proximity between the pontine and thalamic regions.The trigeminal system has features that make it a unique system in which to study functional connectivity of somatosensory pathways in the brainstem from peripheral inputs, intrabrainstem connections, and central projections from the STN. For example, in the trigeminal system, there is a clear distinction of the three trigeminal nerves, as well as the somatotopic and functional segregation present throughout the brainstem and cortex (2,3). Previously, functional magnetic resonance imaging (fMRI) has been used to evaluate activations in the TG and STN to mechanical and thermal stimuli (2-5). Although we and others have begun to use functional and structural observations to investigate changes in the human trigeminal system in clinical populations, a specific and objective method for defining the structural connectivity of the trigeminal system has been lacking (6 -9).The neuronal substrates and axonal pathways that form the human trigeminal system have in large part been anatomically characterized by postmortem histological techniques or contrast-enhanced (CE)-MRI (10 -15). What these methods and observations from these studies cannot easily facilitate is a more direct link between the functional properties of trigeminal neuronal structures defined by functional imaging with the microstructural properties of ...

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