Apinal Cord & Nerve Root Lesions
DDx: Spinal cord lesions
- Infection: EBV, syphilis.
- Inflammation: transverse myelitis, MS, NMO.
- Primary tumour.
- Spinal stroke.
- Degenerative e.g. spino-cerebellar ataxia, Friedrich's ataxia.
- Metabolic: B12 deficiency.
Extrinsic:
- Tumour, either local or metastatic.
- Haematoma
- Abscess
- Trauma
Spine and nerve root anatomy
Spinal cord anatomy
- Grey matter has a butterfly shape. Dorsal horns contain sensory nuclei, and ventral horns contain motor nuclei.
- Surrounding white matter: ascending tracts in dorsal and external lateral cord carry sensory (afferent) info to the brain, and descending tracts in the ventral and internal lateral cord carry motor (efferent) info from the brain.
- See motor problems and sensory problems for more neuroanatomy.
Route of a spinal nerve
- 2 roots exit the spinal column. Dorsal root carries afferent information, and ventral root carries motor information.
- Merge into one spinal nerve and pass through the intervertebral foramen, formed by superior and inferior vertebral notches i.e. it is below the pedicle of the corresponding vertebra.
- Branches into 2 rami. The anterior ramus is larger, and innervates most of the body. The posterior ramus innervates the back.
Injury levels
- The lowest functioning level is the level for a spinal cord injury.
- The lesion itself is often higher than the sensory level, and this is truer the lower down the lesion is. This reflects the fact that nerve roots move down alongside the spine before exiting the spinal cord. For example, T12 sensory level is at the level of the ASIS, even though it is far below the thoracic spine. For this reason, you can never scan too high if a spinal cord lesion is suspected.
Key levels and impairments:
- Phrenic nerve is C3-5, so injury at or above this level may impair ventilation.
- Intercostal muscles are affected by injury above T8.
- Sympathetic trunk exits T1-L2. Injury at or above this level, usually T6 or above, may lead to autonomic dysfunction, including neurogenic shock.
Spinal cord compression
Definition
Causes
- Trauma
- Vertebral crush fracture due to osteoporosis.
- Slipped disc.
- Infection: discitis, epidural abscess, TB.
Neoplastic:
- Usually direct effect of extradural mets: breast, lung, prostate, myeloma, renal cell.
- Can also be secondary to a metastatic vertebral fracture.
- Others: Ewing's sarcoma of the spine, primary CNS cancer (ependymoma, meningioma, glioma).
Signs and symptoms
- Starts with back pain, worse on lying/coughing.
- Rapid progression to symmetrical sensory loss 1-2 dermatomes below lesion (sensory level).
- Then progression to motor weakness (legs), ↑reflexes (may be absent if acute), ↑tone (spastic paraparesis), and sphincter dysfunction (hesitancy, frequency, and later painless retention).
- Have a low threshold of suspicion in a known cancer patient presenting with worsening back pain or impaired mobility/sensation.
Management
- Dexamethasone PO/IV loading dose then daily. Alert neurosurgery.
- MRI whole spine. Spine X-ray is only useful in trauma.
- Definitive treatment is usually with neurosurgery or radiotherapy, though chemotherapy may also have a role in some cases.
Spinal stenosis
Definition
- Spinal degeneration (spondylosis), particularly of the facet joints, resulting in narrowing of the spinal canal. Usually in the lumbar region.
- Affects both cord and roots.
Signs and symptoms
- Neurogenic intermittent claudication: exertional leg pain, with aching and heaviness, spreading from thighs to feet.
- Leg weakness and numbness.
- Back pain (50%) and buttock pain.
- Symptoms worse with lumbar lordosis (standing up, arching back e.g. breast stroke) and relieved by flexion e.g. sitting or lying down, walking up hill. A similar pattern may be seen in facet joint disease (aka facet syndrome), but without leg claudication.
- Cauda equina symptoms or sciatica may also be present.
Management
- Bracing and strengthening exercises.
- NSAIDs
- Epidural corticosteroids.
Surgical:
- Decompression in those with debilitating symptoms.
- Generally improves leg symptoms but not back pain.
- Spinal surgery risks: nerve damage, continued pain, infection, CSF leak.
Conus medullaris and cauda equina syndromes
Conus medullaris syndrome
- Lesions of the tapered end of the spinal cord, at level L1-2.
- Mixed upper-lower motor neuron presentation.
Signs and symptoms:
- Sudden onset, bilateral leg symptoms. Weakness is usually distal, so think spinal cord if proximal.
- Perineal numbness.
- Reflexes: ↑knee but ↓others.
- Early loss of sphincter control → urinary retention and faecal incontinence. Urinary overflow incontinence and constipation can also occur.
- Erectile dysfunction (ED).
- Fasciculations.
Cauda equina syndrome
- Lesions of the intradural roots and nerves below the spinal cord.
- Lower motor neuron presentation.
Signs and symptoms:
- Sudden or gradual onset, bilateral but asymmetrical leg symptoms.
- Saddle (upper inner thigh) and perineal numbness.
- Urinary retention and faecal incontinence. Urinary overflow incontinence and constipation can also occur.
- ↓Reflexes
Relative to conus medullaris syndrome:
- Less back pain but more radicular pain.
- Less ED and later urinary retention
- Less fasciculations but more atrophy.
Management
Radiculopathy
Pathophysiology
- Disc degeneration and herniation.
- Spondylosis (vertebral degeneration) and spondylolisthesis (vertebral displacement).
- Trauma
Signs and symptoms
- Sensory: pain is the hallmark, described as sharp, stabbing, electrical, or hot. May also have numbness or paresthesia in a dermatomal distribution.
- Motor: weak in a myotome.
- Symptoms are usually unilateral.
- If the lesion compresses the spinal cord too, there may also be upper motor neuron signs below that level.
Cervical radiculopathy:
- Neck and upper limb pain symptoms.
Lumbar radiculopathy causes 90% of sciatica (L4-S3):
- Unilateral buttock and leg pain, more than lower low back pain.
- Pain radiates to foot/toes.
- Straight leg raise reproduces pain.
- Numbness and paresthesia.
- They may also have ↓reflexes and muscle weakness e.g. foot drop.
Management
- Refer urgently if there are any back pain red flags.
- Otherwise, initially manage like mechanical back pain: continue ADLs, patient education, physiotherapy, psychological support, no need for imaging. Usually settles within 4-6 weeks.
- Analgesia: start simple (paracetamol and/or NSAIDs), then consider weak opioids. Gabapentinoids often used, but no evidence of benefit.
- For refractory sciatica: consider epidural steroid or local anaesthetic injections if severe, acute, and persists >1-2 weeks; consider MRI and spinal decompression surgery if persists >6-8 weeks. Surgery may improve leg pain but likely not back pain.
- For refractory cervical radiculopathy (>6 weeks) or with objective neurological signs, refer for MRI and possible epidural injections or surgery (e.g. anterior cervical discectomy and fusion).
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