Back Pain and Cauda Equina

Question 1

Examples of back pain causes

Answer 1

-Musculoskeletal back pain
-Prolapsed intervertebral disc
-Cauda Equina Syndrome
-Metastatic spinal cord compression
-Spinal stenosis
-Spondylodiscitis

Question 2

General principles of back pain

Answer 2

-Most back pain is innocent and resolves spontaneously
-The history and examination are heavily standardised
-Radiculopathy and myelopathy are different

Question 3

Describe spinal nerves

Answer 3

Mixed nerves
-Motor fibres (efferent to ventral root0
-Sensory fires (afferent to dorsal root)
-Autonomic fibres (efferent to grey and white rami)
31 pairs

Question 4

Describe cervical vertebral anatomy

Answer 4

1. There is an ‘extra’ C8 nerve root (only 7 cervical vertebra)
2. Pedicle / Nerve Root Mismatch
   =The exiting nerve root beneath the pedicle is one number higher i.e. the C7 nerve root is beneath the C6 pedicle
3. Horizontal orientation of exiting nerve roots
   =Together, this means that a prolapsed disc –irrespective of where it prolapses – will only affect the exiting nerve root one level higher i.e. a prolapsed C6/7 IVD will affect the C7 nerve root

Question 5

Describe cauda equina syndrome nerve supply

Answer 5

-Spinal cord ends at L1/2 IVD
-The cauda equina: L2 – S5 (+ coccygeal nerve),descending to their exiting foramen
-Are all mixed spinal nerves, containing:
=Lower motor neurones
=Sensory information
=Autonomic supply to the:
==Bladder (detrusor)
==Anal sphincters
==Urethral sphincters

-Compression of the cauda equina (usually at L4/5) within the vertebral canal due to a massive space occupying lesion:
=Prolapsed IVD is the most common (~70%) (paracentral 90%, lateral or foraminal prolapse 5%)
=Rare: Tumour (~15%), Trauma (~10%), Haematoma, Infection
-Very rare (~1.5– 3 per 1,000,000)
-Surgical emergency to avoid irreversible neurological damage

Question 6

Describe lumbar anatomy

Answer 6

1. Pedicle / Nerve Root match
   =The exiting nerve root beneath the pedicle is the same number i.e. the L4 nerve root is beneath the L4 pedicle
2. Vertical orientation of exiting nerve roots
   =Spinal cord ends at L1/2 and becomes Cauda Equina
   -These means that, at a single spinal level, there is the:
   =Exiting nerve root laterally
   =Traversing nerve root(s) centrally

Question 7

Presentation of cauda equina

Answer 7

-Autonomic dysfunction
-Perianal sensory changes
-Back pain
-Leg (typically, but not always, bilateral)
-Pain +/- Sensory changes (global)
+/- Weakness (global)
-Saddle anaesthesia
+/- urinary incontinence (overflow, not urge)

-Look: Nil
-Feel: Sensory deficit in all distal dermatomes (lower limbs &peri-anal), Palpable, distended bladder

-Move: Motor deficit in all distal myotomes
-PR:
=Diminished peri-anal sensation
=Reduced anal tone
=Diminished anal wink
=Diminished bulbocavernosus reflex

Question 8

Investigation of cauda equina

Answer 8

-Examination: rectal exam
-ASIA chart
-Bladder scan >200mL (N.B.,<200mL has 97% NPV for CES)
-Emergency MRI (within 2 weeks): lumbar spine without IV contrast/ CT

Question 9

Management of cauda equina

Answer 9

-Emergency surgical decompression (microdiscectomy and/or laminectomy)

Question 10

Red flags for neoplasia

Answer 10

> 50 y/o
-History of Ca.
-Pervasive symptoms
-Worsened with straining
-Systemic features of Ca.
-Thoracic pain

Question 11

Red flags for infection

Answer 11

-Fever
-Diabetes / HIV / Immunocompromise
-TB

Question 12

Red flags of fracture

Answer 12

-Trauma
-Structural abnormalities (i.e., ank. spond.)

Question 13

Yellow flags for poor predictors of poor outcome

Answer 13

-Attitudes
-Beliefs
-Compensation
-Use of medical terminology
-Emotions
-Family
-Work

Question 14

Examination of spine/ back

Answer 14

-Look/ feel// move
=Posture
=Colour changes
=Point tenderness
=ROM

-Lower limb neurology
=Tone
=Myotomes
=Reflexes, including clonus and plantars
=Coordination
=Dermatomes

Question 15

Caudal Equina Examination

Answer 15

-External anal sphincter (Pudendal nerve S2-S4)
=Tone (PR)
=Power
=Reflexes - anal wink and bulbavernosus

-Detrusor (Pelvic plexus S1-3)
=Distended bladder
=Incomplete voiding (high PVRV)

-External urethral sphincter (Pudendal nerve S2-4)
=Cannot ‘hold on

Question 16

Investigation in back pain

Answer 16

-Bedside
=Bladder scan -> post-void residual volume >200mL: PVRV <200mL has an NPV of 97%

-Bloods
=Blood cultures – if ?infection
=Blood gases – if unwell
=Routine – FBC, U&E
=Diagnosis-specific – CRP, tumour biomarkers (?myeloma, ?Breast, ?Prostate)

-Imaging
=XR - if ?fracture or ?tumour
=CT - fractures
=MRI: Lumbo-sacral for ?CES, Whole-spine for ?tumour

-Infection
=Fever
=Diabetes / HIV / Immunocompromise
=TB

Question 17

Describe musculoskeletal pain

Answer 17

-2nd most common reason to visit a doctor
-90% resolves spontaneously within 1 year
-Aetiology - by definition, no clear cause. Possibilities include:
=Muscle strain
=Degenerative disc
=Ligamentous injury
=OA of the facet joints

-Risk factors: Obesity, stress, psychiatric co-morbidities, physically demanding jobs

Question 18

Presentation of MSK back pain

Answer 18

-Pain
=Lumbosacral , sharp and intense for 1 to 2 days, muscle spasm, most recover within 3 months
=No radiation below knee
-Stiffness (difficulty bending)
-No red flags

-Look: nil
-Feel: tenderness in paraspinal muscles +/- SI joints in common
-Move: nil specific/ may have restricted range of motion, muscle tenderness or trigger points
-SLR negative

Question 19

Investigation of MSK back pain

Answer 19

-Clinical
-(MRI first line for most, if imaging required)
-(Lumbar XR useful in trauma or if >70 y/o)

Question 20

Management of MSK back pain

Answer 20

-Non-pharmacological is first line
=Reassurance
=Weight loss
=Normal physical activity
=Heat packs
=Group physio
-Pharma: NSAIDs

Question 21

Describe prolapsed IVD

Answer 21

-Protrusion of the nucleus pulposus through the annulus fibrosus
=Pro-inflammatory -> localised pain
=Compression of: The exiting nerve roots (common) -> radiculopathy, The spinal cord (rare) -> myelopathy

-95% are L4/5 or L5/S1 level (N.B., there is no cord at this level!)
-Aetiology: recurrent torsional strain
-Risk factors: male, occupation, increasing age

Question 22

Types of prolapsed IVD

Answer 22

Paracentral prolapse (90%): affect nerve root below
-Compress the traversing nerve root, leading to symptoms affecting the nerve root ‘below’
=i.e. a paracentral L4/5 IVD prolapse will compress the traversing L5 nerve root (+/- S1)

Lateral/ Foraminal prolapse (5%): affect nerve root at same level
-Compressing the exiting nerve root at the same spinal level
=i.e. a lateral L4/5 IVD prolapse will compressing the exiting L4 nerve root

Question 23

Presentation of Prolapsed IVD

Answer 23

-Pain- typically sudden onset
=Low back pain + Referred pain to the relevant dermatome
+/- weakness in relevant myotome
=No red flags

-Look: Nil
-Feel: Sensory deficit in relevant dermatome +/- paraspinal muscle tenderness
-Move: Motor deficit in relevant myotome
-SLR positive

Question 24

Investigation of prolapsed IVD

Answer 24

-Clinical
-XR often performed initially
-MRI if symptoms >1 month or red flags

Question 25

Management of Prolapsed IVD

Answer 25

-Conservative is first line – 95% improve within 3/12;5% develop chronic symptoms
=Reassurance
=Weight loss
=Normal physical activity
=Heat packs
=Group physio
=NSAIDs
-Second line: Nerve root corticosteroid injection

Question 26

Presentation of spinal metastases and metastatic spinal cord compression

Answer 26

-Pain:
=Thoracic (new) or lumbar (worsening)
=Unremitting (not relieved by lying down)
=Worse with straining
-Leg weakness -> difficulty walking (2/3rds)
-Sensory changes in the lower limbs
-Autonomic dysfunction: Bladder, Bowel

-Below the affected spinal level:
=UMN deficit
=Sensation: diminished
=Reflexes: initially diminished, then hyperreflexia
=Autonomic: bladder dysfunction (initially flaccid paralysis -> evolves to hypertonic bladder over time)

Question 27

Investigation and management of metastatic spinal cord compression

Answer 27

-MRI
-Lie flat and log roll (prevent vertebral collapse)
-Urgent corticosteroid dose (16mgdexamethasone + PPI for gastro protection)
=Unless lymphoma?? NICE
+/- Surgery (decompression and stability)
+/- Radiotherapy

Question 28

Describe spinal stenosis

Answer 28

-Due to degenerative disease of the spine:
=Hypertrophy of these degenerative tissues encroaches on the spinal canal and neural foramina, therefore limiting space for the neural tissues.
=Since this occurs preferentially in the lumbar spine, it is predominantly the cauda equina that is affected
=Leads to neurogenic claudication, can cause cauda equina

Question 29

Presentation of spinal stenosis

Answer 29

-Back pain, worsened by activity
-Leg neurogenic claudication during activity:
=Worse downhill
=Better uphill (c.f., this is the reverse of vascular claudication)
=Relieved by leaning forward / sitting (N.B., stopping doesn’t relieve symptoms)
-Leg paraesthesia, with the same aggravating /relieving factors as above
+/- urinary incontinence (overflow, not urge)

-Characteristically featureless examination
-Occasionally diminished ankle reflex (S1/2) and patellar reflex (L3/4)

Question 30

Neurogenic vs vascular claudication

Answer 30

-N
=Postural changes
=Walking upright, standing stationary causes symptoms
=Sitting, stationary bicycle (back flexed) relieves symptoms
=Up stairs easier

-V
=Walking upright, stationary bicycle causes symptoms
=Standing stationary, sitting relieves symptoms
=Down stairs easier
=Abnormal pulses

Question 31

Investigation of spinal stenosis

Answer 31

-MRI gold standard
-XR -> degenerative changes

Question 32

Management of spinal stenosis

Answer 32

-Conservative: weight loss, PT
-Epidural injections
-(Operative if failure to improve)

Question 33

Describe spondylodiscitis and risk factors

Answer 33

-Acute bacterial infection of the intervertebral disc
=May spread to the vertebral bodies (osteomyelitis) or the epidural space (epidural abscess)
-S. aureus most common organism

-Risk factors:
=Immunosuppression or immunodeficiency
=DM
=IVDU
=Malnutrition

Question 34

Clinical features of spondylodiscitis

Answer 34

-Back pain
-Fever
+/- neurological deficit

Question 35

Investigations of spondylodiscitis

Answer 35

-MRI
-Blood culture
-CT-guided biopsy of BC negative

Question 36

Management of spondylodiscitis

Answer 36

-IV Abx
+/- surgical debridement