Spinal cord and peripheral nerves Flashcards
What comprises the cervical plexus? What are its functions?
C1-4. Branches from the plexus innervate the skin (sensation) and muscles associated with the neck.
What comprises the brachial plexus? What are its functions?
C5-T1 (the last 4 cervical and T1). Branches innervate the skin and muscles action on the upper limb
What comprises the lumbar plexus? What are its functions?
L1 - L4 Branches from the plexus innervate the skin and muscles of the lower abdominal wall in the inguinal region and the anterior and medial compartments of the thigh.
What comprises the Sacral (lumbosacral) plexus? What are its functions?
L4 - S4 is derived from the ventral rami of the 4th and 5th lumbar and first 4 sacral spinal nerves. This plexus has the sciatic nerve as one of its branches. The sacral plexus is responsible for innervation of the skin and muscles of the gluteal region, posterior compartment of the thigh and all of the leg and foot.
Why is it unlikely that injuries to the lower lumbar vertebrae result in direct spinal cord injury?
In the adult the lumbar and sacral spinal roots exit at the appropriate vertebral level but the spinal segments themselves are located between the 10th and 12th thoracic vertebrae.
Table 1 - peripheral nerve damage
Page 92
In the case of a peripheral mononeuropathy; what are the symptoms of an incomplete lesion?
An incomplete lesion such as the entrapment of a nerve within a muscle or compression of a nerve within a bony tunnel will result in partial loss of sensation or paresthesia (tingling) and weakness of those muscles supplied by the particular nerve.
What is a plexopathy?
A plexus lesion
What is a radiculopathy? What symptoms does it produce?
Involve a lesion to a spinal nerve, a dorsal, or a ventral root. It is often associated with burning or tingling pain radiating down a limb in the dermatome of the affected nerve root. Diminished sensation over the dermatome and reduced strength.
What is the straight-leg-raising test useful for?
It is helpful in diagnosing nerve root compression in the lumbosacral region since it results in traction of the nerve roots. If positive the result is a patient’s typical symptoms of radicular pain and sensory abnormalities.
What distinguishes the cervical or brachial (C5-T1) and lumbosacral enlargements (L3 - S2)?
They contain large dorsal and ventral horns. This is because the amount of gray matter is greatest in regions that innervate the limbs. The ventral horns contain lateral motor nuclei that project to limb muscles in addition to the medial motor nuclei that are also seen in non-limb segments.
Describe the distribution of white matter?
There is much less white matter in low sacral than in high cervical spinal cord, this is because as you ascend rostrally through the spinal cord tracts of ascending axons (sensory) receive new incoming axons adding to the size of the white matter.
How can Thoracic spinal cord be distinguished from cervical and lumbar regions?
The presence of the intermediolateral cell group which contains the cell bodies of the preganglionic sympathetic (visceral efferent) neurons and by Clarke’s nucleus, a cerebellar relay nucleus which bulges into the ventrolateral part of the posterior funiculus from T1-L2.
Where is the posterior or dorsal funiculus and what information does it carry?
It lies between the two dorsal horns and carries epicritic information to the brainstem.
Where are the two lateral funiculi and what information do they carry?
They are lateral to the gray matter and between the dorsal horn and the exit of the ventral roots.
