Posterior spinal cord

The epidural space surrounds the dura mater of the spinal cord. It is bounded by the pedicles of the vertebral arches and by the anterior and posterior ligaments connecting the bony vertebral column. The epidural space contains nerve roots, fat, and blood vessels. 

Surgery for spinal cord compression typically involves either laminectomy for posterior lesions or decompression with fixation. Surgery is the treatment of choice for the following patients (1) those with an unstable spine requiring... 

Laminectomy Excision of the posterior arch of a vertebra to relieve pressure on the spinal cord. 

Following the development of the motor program, neurons originating in the multimodal motor association areas transmit impulses by way of association tracts to neurons of the primary motor cortex. The primary motor cortex is located in the precentral gyrus, which is the most posterior region of the frontal lobe adjacent to the multimodal motor association areas (see Figure 6.3) this area initiates voluntary contractions of specific skeletal muscles. Neurons whose cell bodies reside here transmit impulses by way of descending projection tracts to the spinal cord, where they innervate the alpha motor neurons (which innervate skeletal muscles). 

Ataxia An inability to coordinate muscle activity during voluntary movement, so that smooth movements occur. Most often due to disorders of the cerebellum or the posterior columns of the spinal cord may involve the limbs, head, or trunk. 

V.c.1.1. Cyclo-oxygenase inhibition. Inhibition of cyclo-oxygenase reduces the level of circulating prostaglandins and neurogenic inflammation. This is the mechanism of action of nonsteroidal antiinflammatory drugs (NSAID) and aspirin. The mode of action of paracetamol is less clear (inhibition of prostaglandins in the nociceptors of the posterior horn of the spinal cord and action on the supraspinal structures implicated in nociception). 

Measure crown-rump length, number of somite numbers, assess caudal extension, somites (morphology and count), posterior neural tube (primitive spinal cord), anterior neural tube (primitive brain), heart, pharyngeal arches, and facial structures. 

Posterior Neural Tube (Presumptive Spinal Cord)... 

Posterior from the hindbrain, the caudal neural tube gradually tapers into a narrower tube (Fig. 6a). The primitive spinal cord should be relatively straight throughout the axis (score of 5). On occasions, a mild bend associated with normal rotation is observed around the level of the heart and at the forelimb bud (score of 4) (Fig. 6b, arrows). 

Fig. 6. Representative score assignment for the primitive spinal cord (caudal neural tube), (a) Normal primitive spinal cord, which is relatively straight throughout the axis, (b) A primitive spinal cord with a subtle bend arrowy, (c) An illustration of a spinal cord with subtle bends, (d) A primitive spinal cord with mild bends/kinks (bracket), (e) An illustration of a primitive spinal cord with a mild bend (arroW). (f) Multiple marked kinks (arrows) in the spinal cord, (g) An illustration of a primitive spinal cord with multiple marked bends (arrows), (h) Multiple kinks (bracket and bends (arrows) in the spinal cord, (i) An example of caudal neural tube with an enlarged posterior neuropore (circle).

If a spinal cord is cross-sectioned, the gray matter appears as a roughly H-shaped area in its middle which is, divided into dorsal (posterior), lateral, and ventral (anterior) horns. The horns are interconnected by a crossbar, the gray commissure. The rest of the spinal cord is the white matter, made up largely of tracts of myelinated nerve fibers (axons). Ascending tracts carry afferent sensory impulses towards the brain, descending tracts transmit motor impulses from the brain to the motor neurons in the ventral or lateral horns of the gray matter. 

Apart from its role as a major mediator of inflammation and allergic reactions and as physiological regulator of gastric acid secretion, histamine is also a neurotransmitter in the CNS. Central histaminergic cell bodies are located in the posterior hypothalamus and project diffusely to almost all brain regions and to the spinal cord. There are four types of histamine receptors, all G-protein-coupled, Hi, H2, H3 and H4. Hi receptors couple to Gq/11 proteins. H2 receptors couple to Gs. H3 and H4 receptors couple to Gi/o. 

Orexins (also known as hypocretins) and presynaptic receptors activated by orex-ins were first described in 1998 (Figure 1). Orexin-A (hypocretin-1) and orexin-B (hypocretin-2) consist of 33 and 28 amino acid residues, respectively, and are derived from a common precursor molecule (prepro-orexin). They act on two receptors, OXi and OX2. Orexinergic neurones have their perikarya in the lateral and posterior part of the hypothalamus and project to many parts of the brain, including the cerebral cortex, thalamus, limbic system, locus coeruleus and raphe nuclei, and to the spinal cord. Orexin-like immunoreactive neurones also occur in the small intestine (for review, see Smart and Jerman 2002). 

Fig. 17.2. a Superficial arteries of the spinal cord. X-ray film of an injected specimen in a.p. view. The anterior spinal artery system is visible on the ventral surface of the cord, b Intrinsic spinal cord arteries. X-ray microangiogram of a transverse section (lumbar enlargement). The sulcal or central artery within the anterior fissure (arrow) is dominant. Note the posterior and posterolateral spinal arteries at both sides of the posterior root entry zone (arrowheads). AST, anterior spinal artery... 

AVMs of the perimedullary fistula type are direct AV shunts that are located on the ventral or dorsal surface of the spinal cord or the conus medullaris, usually in the thoracolumbar area, occasionally thoracic, and rarely cervical. Their location thus is intradural, intra- or extramedullary. They are always supplied by spinal cord vessels, either by the anterior spinal artery (ventrally) or by a posterolateral artery (dorsally), depending on their location. They drain into spinal cord veins (Fig. 17.12). Drainage may even ascend up to the foramen magnum or into the posterior fossa. 

Spiller W (1909) Thrombosis of the cervical anterior median spinal artery. I Nerv Ment Dis 36 601 Stein SC, Ommaya AK, Doppman JL, Di Chiro G (1972) Arteriovenous malformation of the cauda equina with arterial supply from branches of the internal iliac arteries. Case report. J Neurosurg 36 649-651 Stepper F, Lovblad KO (2001) Anterior spinal artery stroke demonstrated by echo-planar DWI. Eur Radiol 11 2607-2610 Suh T.H., Alexander L (1939) Vascular system of the human spinal cord. Arch Neurol Psychiat 41 659-677 Suzuki T, Kawaguchi S, Takebayashi T, Yokogushi K, Takada J, Yamashita T (2003) Vertebral body ischemia in the posterior spinal artery syndrome case report and review of the literature. Spine 28 E260-264... 

Isolated affection of the spinal cord in PNS is rare. Most often, myelitis is part of the PEM syndrome, with accompanying symptoms from other parts of the nervous system and signs of intrathecal inflammation, such as elevated protein and moderate pleocytosis in the CSF. The myelitis can involve both anterior and posterior columns and can be localized to a few segments or extend to the whole cord [42],... 

Enkephalins are found in varying amounts in nearly all regions of the nervous system, in the posterior lobe of the pituitary, and in the adrenal cortex. They play a role in pain transmission in that they act as transmitters for the pain-inhibiting neurons in the spinal cord. 

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