Anatomy of the Spinal Cord Tracts
- Motor:
- Anterior horn (cell bodies of motor neurons)
- Lateral corticospinal / pyramidal tract
- Begins in primary motor cortex
- Descends on ipsilateral side through thalamus, reaching the medulla
- Crosses at medullary pyramid
- Then descends in contralateral cord
- Sensory:
- Lateral spinothalamic / anterolateral tract (pain and temperature)
- Sensory fibres enter ipsilateral cord via dorsal root
- Immediate decussation across the anterior commissure, just anterior to the central canal
- Thereafter ascends to thalamus in the contralateral cord
- Dorsal column (vibration, pressure, proprioception)
- Ipsilateral on entering cord, ascends on ipsilateral side to ipsilateral cuneate and gracilis nuclei
- Fasciculus cuneatus – upper limb
- Fasciculus gracilis – lower limb
- Second order neurons from these nuclei then decussate and run towards the thalamus (ventral posteromedial nucleus)
- Ipsilateral on entering cord, ascends on ipsilateral side to ipsilateral cuneate and gracilis nuclei
- Lateral spinothalamic / anterolateral tract (pain and temperature)
Segmental Syndromes / Transverse Myelitis
- Acute cord transection will cause spinal shock (flaccid paraparesis, urinary retention, diminished reflexes)
- Thereafter, clinical picture is:
- Sparing of the cranial nerves
- Increased tone (velocity-dependent)
- Hyperreflexia below the level of the lesion
- Upgoing plantars
- Power
- If mechanical, may have LMN weakness at the level of lesion
- Otherwise, pyramidal weakness bilaterally below the level of lesion
- Sensation
- Sensory level in a dermatomal distribution
- Both pinprick and temperature affected
- Look for wheelchair
- Look for surgical scars over the back
- Causes
- Trauma
- Transverse myelitis
- Demyelinating
- Multiple sclerosis
- Neuromyelitis optica
- Idiopathic transverse myelitis
- Acute disseminated encephalomyelitis
- Inflammatory
- Systemic lupus erythematosus
- Sjögren’s syndrome
- Infection
- Bacterial: Lyme, mycoplasma, tuberculosis, syphilis
- Viral: HSV, VAV, CMV, HIV, HAV, echovirus, influenza virus
- Demyelinating
- Tumours
- Epidural abscess
- Degenerative spondylosis
- Investigation
- Magnetic resonance imaging of the spinal cord to look for lesions separated in space
- Lumbar puncture
- Unpaired oligoclonal bands (MS)
- Cytology
- CSF VDRL
- Elevated CSF protein
- Angiotensin converting enzyme (neurosarcoidosis)
- Serology
- NMO antibody (anti-aquaporin-4 antibody) – sensitivity 70%, specificity 100%
- Antinuclear antibody, anti-dsDNA (SLE)
- Anti-Ro/SSA and anti-La/SSB antibodies (Sjogren’s syndrome)
- Management (inflammatory myelitis)
- Multidisciplinary team approach
- Patient education
- IV methylprednisolone
- For severe disease
- IV cyclophosphamide
- Plasma exchange, especially if failed methylprednisolone
- If no improvement after PLEX, some evidence for
- IV immunoglopulin (ADEM)
- Rituximab (NMO)
- Azathioprine (SLE)
- See section on multiple sclerosis
Posterior Cord Syndrome
- Posterior cord syndromes affect the dorsal column and corticospinal tracts
- Clinical findings
- Increased tone below the level of the lesion
- Hyperreflexia below the level of the lesion
- Bilateral pyramidal weakness below the level of the lesion
- Proprioceptive and vibration loss below the level of the lesion
- Spared pinprick sensation
- Causes
- Multiple sclerosis (cerebellar signs, INO, RAPD)
- Tabes dorsalis (Argyll-Robertson pupils)
- Sub-acute combined degeneration of the cord from B12 deficiency (absent ankle jerks, macroglossia)
- Friedrich’s ataxia (cerebellar signs, pes cavus, kyphoscoliosis)
- Epidural / intramedullary tumours
- Cervical myelopathy
- Atlanto-axial subluxation
Anterior Cord Syndrome
- Anterior cord syndromes affect the spinothalamic and corticospinal tracts
- Clinical findings
- Increased tone below the level of the lesion
- Hyperreflexia below the level of the lesion
- Bilateral pyramidal weakness below the level of the lesion
- Loss of pain and temperature bilaterally below the level of lesion
- Proprioception and vibration spared
- Causes
- Anterior spinal artery infarction
- Intervertebral disc herniation
- Radiation myelopathy
Brown-Sequard Syndrome
- Hemisection of the cord affecting the corticospinal, dorsal column and spinothalamic tracts
- Unlike most cord syndromes, this causes a hemiparesis
- Clinical findings
- Spares all the cranial nerves
- Ipsilateral increased tone below the level of the lesion
- Ipsilateral hyperreflexia below the level of the lesion
- Ipsilateral pyramidal weakness
- Ipsilateral loss of proprioception and vibration below the level of the lesion
- Contralateral loss of pain and temperature below the level of the lesion
- Causes
- Demyelination
- Trauma
- Spinal cord tumours
- Longitudinal myelitis
Central Cord Syndrome / Synringomyelia
- Central lesions affect the decussating nociceptive fibres first, then the anterior horn cells and corticospinal tracts; the dorsal columns are usually spared
- Clinical findings
- Inspection
- Wasting at the level of the lesion
- Spasticity below the level of the lesion
- Reflexes
- Increased below the level of the lesion (if large enough to affect corticospinal tract)
- May be absent at the level of the lesion
- Plantars may be extensor
- Power
- Flaccid weakness at the level of the lesion (anterior horn cell)
- Pyramidal below the level of the lesion (corticospinal tract)
- Sensation
- Bilateral pain and temperature loss around the level of the lesion
- Normal pain and temperature above and below the level of the lesion
- Normal proprioception and vibration sense
- Inspection
- Causes
- Syringomyelia
- Intramedullary tumours
Pure Motor Syndrome (Spastic Paraparesis)
- Clinical picture
- Walking aids / wheelchair
- Disuse atrophy
- Increased tone, usually in the lower limbs first
- Hyperreflexia
- Pyramidal weakness below the level of the lesion
- Sensation usually intact
- Some forms of hereditary spastic paraplegia may involve mild dorsal column loss
- Causes
- Human T cell lymphotropic virus-1 (HTLV1, tropical spastic paraparesis)
- Retrovirus which infects CD4 T cells
- Transmission: vertical, sexual, contaminated blood products
- Often in Africa, South America and southern Japan
- Also causes adult T cell leukaemia / lymphoma
- Lifetime risk of haematological or neurological events in carriers: 0.25 – 3%
- Usual onset 40 – 50, more common in women
- Onset usually asymmetric and gradual, with gait and urinary disturbance
- May have brisk upper limb reflexes
- Hereditary spastic paraplegia
- Almost 50 gene loci
- De novo mutations are frequent
- May be inherited in autosomal dominant, autosomal recessive or X-linked pattern
- Autosomal dominant is most common
- Phenotype and penetrance is variable – determining family history may be difficult
- Usually presents in the fourth decade (range of first till seventh decade)
- Spastic paraparesis, usually of the lower limbs
- 30% have dorsal column involvement
- 30% have neurogenic bladder
- Primary lateral sclerosis (see Motor Neurone Disease)
- Human T cell lymphotropic virus-1 (HTLV1, tropical spastic paraparesis)
- Investigation
- Peripheral blood film
- Atypical T lymphocytes with convoluted nuclei – “flower cells” (HTLV1)
- HTLV1 antibodies in CSF and serum
- Genetic testing for hereditary spastic paraparesis (most common is spastic paraplegia gene 4)
- Peripheral blood film
- Management
- Multidisciplinary team approach
- HTLV
- Transient improvement with corticosteroids
- Combivir (lamivudine + zidovudine) may decrease viral load, no evidence for effect on neurological function
Conus Medullaris Syndrome
- Lesion at L2 affecting the conus medullaris (tapered end of spinal cord)
- Clinical picture
- Often sudden, bilateral onset of symptoms with lower back pain
- Normal knee jerks, but absent ankle jerks
- Flaccid paralysis bladder and rectum
- Saddle anaesthesia
- Leg weakness may be mild, or predominantly distal
- Causes
- Epidural abscess
- Tumour at L2
- Intervertebral disc herniation at L1/2
Cauda Equina Syndrome
- Compression of the cauda equina, containing 18 nerve roots (L2 – S5)
- Clinical picture
- Lower back pain radiating to legs
- Wasting, usually no fasciculations
- Arreflexia in the legs (ankles affected first)
- Weakness
- Ankle plantarflexion (S1/S2)
- Knee flexion (L5/S1)
- Hip extension (L5/S1)
- May involve more muscle groups as compression worsens
- Sensory loss in all modalities in dermatomes supplied by affected roots
- May have urinary retention, lax anal tone (must do digital rectal examination)
- Causes
- Intervertebral disc herniation
- Epidural abscess
- Epidural tumor
- Intradural extramedullary tumour
- Carcinomatous meningitis
- Bony metastases
- Investigation
- Magnetic resonance imaging of the lumbosacral spine
- Management
- Emergency radiotherapy
- Steroids (dexamethasone 16mg daily in divided doses)
- Neurosurgical referral for surgical decompression and stabilization