Spinal Cord Syndromes
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Direct answer
Spinal cord syndromes are patterns of motor and sensory loss that localise a lesion to one side, one column or one region. Brown-Sequard syndrome is a hemisection pattern, with ipsilateral weakness and loss of proprioception below the lesion and contralateral loss of pain and temperature. Anterior cord syndrome spares posterior column sensation, central cord syndrome spares the sacral segments, and subacute combined degeneration reflects vitamin B12 deficiency.
What you must remember
- Brown-Sequard: ipsilateral upper motor neuron weakness and dorsal column loss below the lesion, with contralateral pain and temperature loss starting one or two segments below.
- Anterior spinal artery: bilateral motor loss and loss of pain and temperature below the level, with vibration and position sense preserved.
- Central cord: hyperextension injury or syringomyelia; arm weakness and sensory loss exceed leg involvement, with sacral sparing.
- Subacute combined degeneration: dorsal column and lateral corticospinal involvement from vitamin B12 deficiency, causing vibration loss, spastic gait and a positive Romberg sign.
- Lhermitte sign: electric shock down the spine on neck flexion, seen in cervical cord lesions, multiple sclerosis and B12 deficiency.
- Dissociated sensory loss: pain and temperature lost while touch is preserved, pointing to a central lesion such as syringomyelia.
- Tabes dorsalis: neurosyphilis causing posterior column loss, sensory ataxia, Argyll Robertson pupils and Charcot joints.
A deficit pattern walked back to a cord level
A 45-year-old man has a stab wound to the right side of the lower neck. He now has right leg weakness, loss of vibration and position sense on the right, and loss of pain on the left from about two segments below the wound.
- Motor pathway: Corticospinal fibres cross in the medulla, so weakness appears on the same side as the lesion.
- Proprioception pathway: Dorsal column fibres ascend on the same side and cross higher up, so proprioceptive loss is also ipsilateral.
- Pain and temperature pathway: Spinothalamic fibres cross within a segment or two of entry, so pain and temperature loss appears on the opposite side and starts just below the lesion.
- Confirm the level: Reflexes, plantar responses, the sensory level and bladder and anal tone are then checked to confirm the level.
- Sudden bilateral picture: For a sudden bilateral picture with preserved vibration, an anterior spinal artery infarct is the diagnosis to consider, classically after aortic surgery or hypotension.
- Slow limb ataxia: For a slowly progressive limb ataxia with spasticity and a low B12 level, subacute combined degeneration is the answer. Intramuscular hydroxocobalamin should begin without waiting for spinal imaging.
Where the anatomy trap catches students
Most errors come from a few predictable confusions.
- Trap: putting both sensory modalities on the same side in Brown-Sequard syndrome Correct: vibration and position sense are lost on the lesion side, while pain and temperature are lost on the opposite side, and examiners often reverse the pair.
- Trap: mistaking anterior cord syndrome for a complete transection Correct: the preserved vibration sense separates it from a complete transection, which is why it is a favourite trap.
- Trap: waiting for a gait change before suspecting subacute combined degeneration Correct: vibration loss may appear before any gait change, and the MCV is often raised. Nitrous oxide inactivates cobalamin, so a patient who abuses it can develop a B12-like picture without low serum levels initially.
- Trap: calling central cord syndrome in an older person after a fall a syrinx Correct: it points to a hyperextension injury, not a syrinx.
Frequently asked questions
Which side is the motor deficit in Brown-Sequard syndrome?
Brown-Sequard syndrome produces ipsilateral upper motor neuron weakness and proprioceptive loss below the lesion, on the same side as the hemisection. Pain and temperature are lost on the opposite side because the spinothalamic fibres cross within a segment or two of entry.
Why is proprioception preserved in anterior spinal artery syndrome?
Anterior spinal artery syndrome spares proprioception and vibration because the dorsal columns are supplied by the posterior spinal arteries, which are unaffected. The anterior two-thirds of the cord, including the corticospinal and spinothalamic tracts, is infarcted, so motor loss and loss of pain and temperature occur below the level.
What bladder and sensory pattern is typical of central cord syndrome?
Central cord syndrome causes greater weakness in the arms than the legs, with variable sensory loss in the upper limbs. Bladder dysfunction is common, while sacral sensation is usually spared. It is typically seen after hyperextension injury in older people with cervical spondylosis.
Which tests confirm subacute combined degeneration?
Subacute combined degeneration is confirmed by a low serum vitamin B12 level, raised methylmalonic acid and homocysteine, and sometimes anti-intrinsic factor antibodies. Spinal MRI may show posterior column signal change, but intramuscular hydroxocobalamin should not wait for imaging.