Posterior Spinocerebellar Tract Originates in thoracic and upper lumbar regions. Consists of uncrossed fibers that enter cerebellum through inferior cerebellar peduncles. Transmits ipsilateral proprioceptive information to cerebellum.
Anterior Spinocerebellar Tract Originates in lower trunk and lower limbs. Consists of crossed fibers that recross in pons and enter cerebellum through superior cerebellar peduncles. Transmits ipsilateral proprioceptive information to cerebellum.
Blood Supply of Spinal Cord
BLOOD SUPPLY OF SPINAL CORD
The spinal cord is supplied by 1. Anterior spinal artery 2. Posteriorspinalartery3. Spinal branch from the 1st intercostal artery4. Spinal branch from the 11th intercostal artery Branches of the vertebral, deepcervical, intercostal, and lumbararteries contribute to three arteries that run the length of the spinal cord; the anterior spinal and the two posterior spinal arteries. Anterior spinal artery The anterior spinal artery is the larger It is a midlineartery – lies on the anterior median fissure It is formed at the foramen magnum by union of two arteries onefromeachvertebralartery Supplies the spinal cord anterior part namely the lateral columns and the anterior grey and white columns The posterior spinal arteries One or two on each side – derived from the vertebralartery (or from inferior cerebellar artery) at the level of foramen magnum Both the anterior and the posterior spinal arteries descend from the level of the foramen magnum
21 pairs of segmental radicular arteries supply the nerve roots and about half of them contributeto the spinal arteries.
The arteries of Adamkiewicz Spinal branches (segmental radicular arteries) from the 1st and 11th intercostal arteries are large (T1 & T11) They pass along the nerve roots to the spinal cord and reinforce the anterior and posterior spinal arteries supplies the lower thoracic and upper lumbar parts of the cord. Spinal artery at T1 (Adamkiewicz) supplies the cord only downwards Spinal artery at T11 (Adamkiewicz) supplies the cord both above and below (radicularis magna)
Abnormal situation e.g. high take off – the iliac artery branch supplies the lower thoracolumbar region of the cord entering through intervertebral foramen of L4-5
Generally the proportion of flow is greatest from the raducularis magna “feeder” artery to the thracolumbar region. In abnormal situations ( e.g. high take-off) the iliac artery branch may supply the lower thoracolumbar region of the cord entering by way of the intervertebral foramen in the vicinity of L4-5
Spinal Veins Spinal veins form plexuses anteriorly and posteriorly On each side the spinalveins are double, straddling the posterior nerve roots All of them draininto vertebralveins in the neck, azygos veins in the thorax, lumbar veins in the lumbar region, lateral sacral veins in the sacral region through intervertebral foramina
Venous Drainage of the Spinal Cord This is by 6 irregular, plexiform channels . There is one along the anterior and posterior midlines; Along the line of attachment of the dorsal roots of each side; Along the line of attachment of the ventral roots of each side. These are drained by the radicular veins. Each, in turn empty into the epidural venous plexus.
MOTOR SYSTEM -stiffness of legs and tripping of toes –s/o UMN lesion -buckling of knees ,wasting or fasciculations –s/0 LMN lesion -UMN signs will be below the level of lesion-hypertonia ,spasticity ,clonus ,brisk reflexes .pl.extensor -LMN signs –muscle wasting ,fasciculations sensory loss ,tender muscles ,
UMN signs –early with extramedullarylesions,late with intramedullary lesions Both UMN,LMN signs –with intramedullarylesions,MND, Symmetrical upper and lower girdle muscle involvement with myalgia-inflm.myopathies Asymmetrical distal and proximal muscle involvement –inlcusion body myositis Delayed relaxation of muscles,-myotonic disorders Episodic attacks of flaccid weakness –hypokalemic periodic paralysis
SENSORY SYSTEM --radicular pain-lancinatingdermatomal pain ,increased by cough, sneeze ,common with extradural lesions --vertebral pain ,aching ,localised to spine involved –neoplastic or inflammatory extradural lesions --funicular pain-deep ,illdefineddysaesthesia,due to intra-medullary lesions
Spinal cord-loss of pain&temp. over the opp.side,if AL funiculus involved -loss of position ,vibration sense if dorsal funiculus involved -sacral sparing if lesion is deep Dorsal root-radicular pain &sensory loss over the dermatome Dorsal root ganglion –diffuse pansensoryloss,with sensory ataxia Peripheral neuropathy-paresthesia,tingling sensation ,over the distribution without sensory loss Polyneuropathy-distal symm.sensory loss
Descending progression of paresthesia –intramedullary lesion Ascending progression of paresthesia –extramedullary lesions Definite sensory level of pain and temp.- extramedullary lesions(Brown-sequard) Dissociated sensory loss - intramedullary lesion