Session 2 - The Spine Flashcards
Define the term dermatome and describe the embryonic development of dermatomes
Dermatome - area of skin that is supplied by a single spinal nerve
Embryonic development:
From day 20, paraxial mesoderm differentiates into segments called somites. The somites are comprised of a ventral and a dorsal portion. The ventral portion consists of sclerotome, the precursor to the ribs and vertebral column. The dorsal portion consists of dermomyotome.
Over time, the myotome proliferates and the dermatome disperses to form dermis. As the limbs grow, the dermis associated with the precursor of the limbs is stretched and moved down the limb, creating the segmental innervation.
Describe the composition and formation of a mixed spinal nerve
Mixed spinal nerves are parallel bundles of axons encased in connective tissue, containing both motor and sensory nerves (plus autonomic nerves)
Formation:
Dermatomyotomes develop in association with a specific neural level of the spinal cord and take a nerve supply with them from neural tube
Define the terms myotome and motor unit and describe the embryonic development of myotomes
Myotome - a group of muscles supplied by a single spinal nerve (or spinal nerve root) (contains many motor units)
Motor unit - is a motor neurone and the skeletal muscle fibres it innervates
Embryonic development:
From day 20, paraxial mesoderm differentiates into segments called somites. The somites are comprised of a ventral and a dorsal portion. The ventral portion consists of sclerotome, the precursor to the ribs and vertebral column. The dorsal portion consists of dermomyotome. Over time, the myotome proliferates and eventually develops into muscle
Define the term ‘neural level’
The neural level is defined as the lowest level of full sensation and motor function
Describe the gross structure and arrangement of the vertebral column
33 vertebrae: 7 cervical = lordosis 12 thoracic = kyphosis 5 lumbar = lordosis 5 (fused) sacrum = kyphosis 4 (fused) coccyx = kyphosis
Describe the structure of the major joints of the vertebral column
- Left and right superior articular facets articulate with the vertebra above
- Left and right inferior articular facets articulate with the vertebra below
The joints between the articular facets, called facet joints, allow for some gliding motions between the vertebrae. They are strengthened by several ligaments
- Vertebral bodies indirectly articulate with each other via the intervertebral discs - cartilaginous joints, designed for weight-bearing. The articular surfaces are covered by hyaline cartilage, and are connected by the intervertebral disc.
State how the structure of the various vertebrae and their associated ligaments help to maintain the stability of the vertebral column
The angles of the articular facets can limit the range of movement for different parts of the spine which helps to stabilise the movement
Ligaments - provide stability by preventing excessive movement between the vertebrae:
Ligamentum flavum – extends between lamina of adjacent vertebrae
Interspinous and supraspinous – join the spinous processes of adjacent vertebrae. The interspinous ligaments attach between processes, and the supraspinous ligaments attach to the tips
Intertransverse ligaments – extends between transverse processes
Describe patterns of normal and an example of abnormal curvature of the spine
Normal curvature: Cervical = lordosis Thoracic = kyphosis Lumbar = lordosis Sacrum = kyphosis Coccyx = kyphosis
Abnormal curvature:
- During pregnancy - excess lumbar lordosis
Describe the anatomical approach when performing a lumbar puncture (i.e. what vertebral level you enter and the layers you need to go through)
Vertebral level you enter:
- L2/3, L3/4, L4/5 - basically below the conus medullaris below the spinal cord to limit the chance of neurological damage (nerves can move out of the way
Layers to go through: SSS ILDEAS
- Skin
- Subcutaneous fat
- Supraspinous ligament
- Interspinous ligament
- Ligamentum flavum (resistance)
- Dura matter
- Epidural fat and veins
- Arachnoid matter
- Subarachnoid space
Define the term ‘neural level’ anatomically and clinically
Anatomical ‘neural level’:
- The central nervous system is segmented throughout its length with each neural segment being known anatomically as a neural level
Clinical ‘neural level’:
- The neural level is the lowest level of fully intact sensation and motor function
Describe the pathophysiology and clinical features of Mechanical back pain
Pathology:
- Generally from poor posture and excessive force throughout the neck and lumbar spine
- Pressure on intervertebral discs whilst slouching causes the discs to be pushed posteriorly (risk of prolapse)
Clinical features:
- Intermittent pain
- Pain worsens with exercise and is relieved by rest
- Pain when the spine is loaded
Describe the pathophysiology and clinical features of Cauda equina syndrome
Pathology: lots of different causes
- Cancer
- Trauma
- Spinal stenosis
- Epidural haematoma
- Epidural abcess
- Prolapased disc
- Spinal haemorrhage
Clinical features: 5 red flag symptoms
- Bilateral sciatica (normally unilateral)
- Perineal numbness
- Bladder/bowel dysfunction
- Painless retention of urine
- Erectile dysfunction
Describe the pathophysiology and clinical features of Prolapsed intervertebral discs
Pathology:
- Protrusion of the nucleus pulpous into the spinal canal leading to compression of the nerve roots
- 4 different degrees/types (degeneration, prolapse, extrusion, sequestration)
- Most commonly occurs at level of L4/5 or L5/S1 due to the amount of loading at base of spine
Clinical features:
- Bladder/bowel incontinence
- Numbness in the genital area
- Erectile dysfunction
- Numbness, pins and needles, or tingling in one or both arms or legs
- Not all slipped discs cause symptoms. Many people will never know they have slipped a disc
Describe the pathophysiology and clinical features of Radicular leg pain (sciatica)
Pathology:
- Pain caused by irritation or compression of one or more of the nerve roots which contribute to the sciatic nerve
Clinical features:
- Pain experienced in back and buttock and radiates to the dermatome supplied by the affected nerve root
Describe the pathophysiology and clinical features of Neurogenic claudication
Pathology: symptoms rather than a diagnoses
- Compression of nerve roots (perhaps due to disc bulging etc.) in the lumbosaccral spinal cord
- Venous engorgement of nerve roots during exercise
- Reduced material inflow
- Pain and paraesthesia
Clinical features:
- Pain in legs whilst walking
- Tingling or cramping in the lower back and one or both legs, hips, and buttocks
- Symptoms are especially present when standing upright or walking and usually relieved with leaning forward or sitting down
