3. The spine - clinical conditions

Question 1

where do you perform a lumbar puncture

Answer 1

L4/5 or L3/4 - i.e. after spinal cord has ended and cauda equina starts at L1/2 - only mobile spinal nerve roots so least chance of neurological damage

Question 2

which structures does the lumbar puncture needle pass through

Answer 2

skin… subcutaneous tissue… supraspinous ligament… interspinous ligament… ligamentum flavum (large give)… epidural fat and veins… dura mater (final give)… arachnoid matter… subarachnoid space

Question 3

why does loss of height occur with ageing

Answer 3

poorer repair of proteoglycans in IV discs… chains shorter and less hydrophilic… water loss from discs (nucleus pulposus dehydration)… discs lose height and pressure

Question 4

describe how ageing can cause mechanical back pain

Answer 4

nucleus pulposus dehydration and decreased IV disc height:

1. load stresses on IV discs alter… reactive ‘marginal osteophytosis’ (growth of syndesmophytes inside ligaments of intervertebral joints) = spondylosis deformans, senile ankylosis
2. increased stress on facet joints… OA
3. decreased size of intervertebral foramen and compression of spinal (segmental) nerves

Question 5

describe the 4 degrees of IV disc herniation

Answer 5

1. disc degeneration - nucleus pulposus dehydration due to ageing
2. disc prolapse - protrusion of nucleus pulposus with slight impingement into spinal canal (with tear in annulus fibrosus)
3. extrusion - nucleus pulposus breaks through annulus fibrosus, but remains within disc space
4. sequestration - nucleus pulposus breaks through annulus fibrosus and separates from main body of disc in spinal canal

Question 6

what are the 3 types of disc prolapse and how common are they

Answer 6

1- paracentral (96%)
2- far lateral (2%)
3- canal filling (larger fragment comes out compressing whole of cauda equina, CES) (2%)

Question 7

which nerve roots are irritated by paracentral and far lateral disc herniations

Answer 7

paracentral: doesn’t affect exiting nerve root of that disc as it has already exited, but rather the traversing nerve root below (e.g. L5 root in L4/5 disc)

far lateral: exiting nerve root (e.g. L4 root in L4/L5 disc)

Question 8

where does disc prolapse most commonly occur

Answer 8

L4/5 or L5/S1 (area of greatest compression)

Question 9

what is sciatica, what is most common cause

Answer 9

compression of any nerve root which contributes to sciatic n.: L4, L5, S1, S2 and S3

most common cause = disc prolapse (so S2 and S3 rarely involved as sacral vertebrae are fused)

Question 10

what is typical distribution of pain in sciatica dependent on?

Answer 10

1. dermatomal distribution of compressed n.
2. course of nerve itself: n. root injury causes venous engorgement, local ischaemia of n., inflammation, etc… resulting irritation causes ectopic n. impulses perceived as pain along course of n,.
3. development of spontaneous contractions in muscle fibres supplied by n. … deep muscular pain in addition to neuropathic pain

Question 11

describe the distribution of pain and paraesthesia caused by compression of L4 nerve root

Answer 11

• pain: anterior thigh, anterior knee, medial aspect of leg

- paraesthesia (only involves dermatome): medial leg

Question 12

describe the distribution of pain and paraesthesia caused by compression of L5 nerve root

Answer 12

• pain: lateral thigh, lateral calf, dorsum of foot, great toe
• paraesthesia: lateral leg + dorsum of foot

Question 13

describe the distribution of pain and paraesthesia caused by compression of S1 nerve root

Answer 13

• pain: posterior thigh, posterior calf, heel and sole of foot
• paraesthesia: lateral border and sole of foot

Question 14

what is cauda equina syndrome

Answer 14

compression of cauda equina by canal-filling prolapsed disc, affecting lumbar and sacral nerve roots

Question 15

describe the presentation of CES

Answer 15

1. bilateral sciatica
2. perianal numbness (compression of S3, S4 and S5)
3. painless retention of urine (loss of sphincter control)
4. urinary/faecal incontinence

Question 16

what is spondylolysis

Answer 16

unilateral or bilateral defect (commonly due to stress fracture but may be congenital defect) in pars interarticularis

most commonly affects L5/S1 causing pain and often precedes spondylolisthesis

Question 17

what is spondylolisthesis

Answer 17

anterior slippage of 1 vertebra over another

Question 18

describe the 5 forms of spondylolisthesis

Answer 18

1. ISTHMIC (most common): defect/fracture of pars interarticularis, usually acquired in adolescence as consequence of spondylosis
2. DEGENERATIVE: in elderly, as result of facet joint OA and bone remodelling
3. DYSPLASTIC (rare): congenital abnormality in shape of facet joints
4. PATHOLOGICAL: from metastases or metabolic bone disease
5. IATROGENIC or TRAUMATIC

Question 19

why is the presentation of isthmic and degenerative spondylolisthesis different

Answer 19

• fracture of posterior vertebral arch in isthmis, so no nerve root compression - predominantly present with back pain
• posterior vertebral arch is intact in degenerative, causing lumbar canal stenosis - Ps present with neurogenic claudication

Question 20

what is lumbar canal stenosis

Answer 20

spectrum of narrowing of spinal canal due to ageing, involving:

• disc bulge
• facet joint OA
• ligamentum flavum hypertrophy and substance deposition

can be secondary to degenerative spondylolisthesis

Question 21

what is the main sign of lumbar canal stenosis

Answer 21

neurogenic claudication (1 or both legs)

Question 22

what is neurogenic claudication and how is this different to intermittent vascular claudication

Answer 22

• pain and weakness in calves, buttocks and/or thighs when walking, which is relieved by rest
• differentiated from intermittent vascular claudication as pain is classically relieved by change in position or flexion of waist

Question 23

describe the pathophysiology of neurogenic claudication

Answer 23

walking increases blood supply to lumbar n. roots, but less scope for venous drainage as n. are compressed in narrowed spinal canal… venous engorgement which further compresses n. roots… reduced arterial flow and transient ischaemia… pain/paraesthesia in legs on exercise, relieved by rest

Question 24

what is spina bifida

Answer 24

neural tube defect occuring during embryological dev. - vertebral arch of spinal column either incompletely formed or absent

most commonly found in lumbar region

Question 25

what is scoliosis

Answer 25

abnormal lateral curvature of vertebral column

can be congenital, idiopathic or neuromuscular

Question 26

what is kyphosis

Answer 26

anterior flexion curvature of spine (abnormal if >40 degrees in thoracic spine)

Question 27

what is lordosis

Answer 27

posterior flexion curvature of spine