Spinal Cord Disorders

Compressive (extrinsic) causes

• Degenerative spondylosis: disc–osteophyte complex and ligamentum flavum hypertrophy narrow the canal, producing chronic cervical myelopathy or lumbar neurogenic claudication; the commonest non-traumatic myelopathy in older adults.
• Neoplastic epidural compression: hematogenous metastases to vertebral body (breast, lung, prostate, myeloma, renal) expand posteriorly into the epidural space.
• Infectious/hemorrhagic: epidural abscess (Staphylococcus aureus most often) and spontaneous epidural hematoma, both of which compress by mass effect within a rigid canal.
• Disc herniation at L4–S1 causing cauda equina compression.

Intrinsic (intramedullary) causes

• Cavitary: syringomyelia, most often associated with Chiari I malformation, and post-traumatic or post-arachnoiditis syrinx.
• Degenerative motor neuron disease: ALS (sporadic in ~90%; familial forms include SOD1 and C9orf72).
• Nutritional/toxic: B12 deficiency causing subacute combined degeneration; copper deficiency and nitrous oxide abuse produce an identical picture.
• Inflammatory/demyelinating: MS, MOG- and aquaporin-4–associated (NMOSD) transverse myelitis.
• Infectious myelitis: HIV vacuolar myelopathy, HTLV-1, tertiary syphilis (tabes dorsalis), varicella-zoster.
• Vascular: anterior spinal artery infarct, classically after aortic cross-clamping or dissection; dural arteriovenous fistula.

• Primary injury mechanisms: Spinal cord injury involves mechanical trauma causing immediate axonal disruption, loss of neuronal membrane integrity, and direct tissue destruction. In non-traumatic conditions, pathophysiology varies by etiology (demyelination, ischemia, infection, compression, or infiltration).

• Secondary injury cascade: Follows primary injury within minutes to hours; includes excitotoxicity from glutamate release, influx of calcium and sodium ions, mitochondrial dysfunction, free radical formation (oxidative stress), inflammatory cell infiltration, and activation of apoptotic pathways. This cascade expands the initial injury zone and is a therapeutic target.

• Vascular compromise: Disruption of spinal cord blood supply leads to ischemic injury; anterior spinal artery syndrome causes infarction of the ventral 2/3 of the cord (affecting motor tracts and spinothalamic tract) while sparing dorsal columns. Edema formation compounds tissue damage through increased intracranial pressure within the rigid spinal canal.

• Demyelination mechanisms: In conditions like multiple sclerosis and acute demyelinating myelitis, autoimmune attack strips myelin sheaths from axons, impeding saltatory conduction. Oligodendrocyte death and complement-mediated inflammation propagate demyelination.

• Tract-specific dysfunction: Lesion location determines which tracts are affected—corticospinal tracts (motor/upper motor neuron signs), dorsal columns (proprioception/vibration), spinothalamic tract (pain/temperature), and autonomic fibers (bladder/bowel dysfunction).

• Spinal shock: Immediately following acute SCI, spinal reflexes below the lesion are abolished, causing flaccid paralysis and areflexia despite upper motor neuron lesion. This resolves over weeks to months as reflex arcs recover, replaced by hyperreflexia and spasticity (return of lower motor neuron reflexes with upper motor neuron control lost).

• Motor deficits: Upper motor neuron (UMN) signs appear below a complete lesion (hyperreflexia, spasticity, positive Babinski, weakness with increased tone). Distinguish from lower motor neuron (LMN) signs at the level of the lesion itself (fasciculations, atrophy, decreased reflexes, flaccid weakness). Acute presentations may initially show flaccid paralysis during spinal shock phase.

• Sensory level: Classically present with a distinct sensory level below which pain and temperature sensation are lost (indicating spinothalamic tract involvement). Dorsal column involvement causes loss of vibration and proprioception, often with preserved pain/temperature sensation (dissociated sensory loss depending on lesion pattern).

• Anterior cord syndrome: Results from anterior spinal artery occlusion or ventral cord compression; presents with bilateral motor paralysis, bilateral loss of pain/temperature sensation, but PRESERVED vibration and proprioception (dorsal columns spared). Classic presentation in flexion-distraction injuries or arterial occlusion.

• Brown-Séquard syndrome: Ipsilateral motor and dorsal column loss; contralateral spinothalamic (pain/temperature) loss due to hemisection of spinal cord. Classically seen with penetrating trauma (stab wounds) or unilateral cord compression. Prognosis is often better than complete lesions.

• Central cord syndrome: Bilateral upper extremity weakness greater than lower extremity weakness with cape-like distribution of sensory loss (affecting central gray matter and crossing spinothalamic fibers). Typically follows hyperextension injuries in elderly patients with pre-existing cervical spondylosis. Often has favorable prognosis with conservative management.

• Posterior cord syndrome (rare): Isolated loss of vibration and proprioception with preserved motor function and pain/temperature sensation; seen with dorsal column pathology (e.g., tabes dorsalis, B12 deficiency, Friedreich ataxia).

• Conus medullaris syndrome: Affects sacral cord (S3-S5); presents with saddle anesthesia, bilateral leg pain, loss of perianal sensation, and early bladder/bowel dysfunction. Distinguishing feature: symmetric bilateral presentation with early autonomic involvement. Emergency decompression indicated.

• Cauda equina syndrome: Affects nerve roots below cord termination (L1-2); presents with asymmetric leg pain (radicular quality), asymmetric leg weakness, asymmetric sensory loss, and late or incomplete bladder symptoms. Critical distinction from conus: asymmetry and preservation of anal tone initially. Surgical emergency with 48-hour window for optimal recovery.

• Autonomic dysfunction: Neurogenic bowel and bladder (retention initially, then reflex emptying), neurogenic orthostatic hypotension, autonomic dysreflexia (dangerous hypertensive response to stimuli below lesion in spinal shock recovery phase).

• Respiratory involvement: Cervical cord lesions at C3-C5 level may cause diaphragmatic paralysis (phrenic nerve involvement); C1-C2 lesions cause complete respiratory failure requiring mechanical ventilation.

• Imaging—MRI (gold standard): High sensitivity for detecting spinal cord edema, hemorrhage, compression, demyelinating lesions, and intramedullary pathology. T2-weighted sequences show cord signal changes; T1-weighted post-gadolinium for contrast enhancement suggesting inflammation or breakdown of blood-brain barrier. MRI indicated emergently in all acute SCI to assess severity and guide triage for surgery.

• Imaging—CT: Useful for detecting bony fractures, subluxation, and acute hemorrhage. Often used first for acute trauma due to speed and availability; rapidly acquired to clear C-spine. CT myelography if MRI contraindicated.

• Neurological examination and ASIA Impairment Scale (AIS)**: Standardized assessment of motor (0-5 grading scale per myotome) and sensory (0-2 scale for light touch/pinprick per dermatome) function. Complete SCI = no motor/sensory function in sacral segments (S4-S5); Incomplete SCI** = sacral sparing present (preserved sensation or voluntary anal contraction). Critical for prognostication and comparing changes over time.

• CSF analysis: Lumbar puncture indicated if demyelinating disease, infection, or hemorrhage suspected. Elevated protein with normal glucose suggests demyelination or malignancy; elevated glucose with elevated protein and pleocytosis suggests bacterial infection; bloody CSF indicates hemorrhage (xanthochromia on examination).

• Electromyography/Nerve conduction studies (EMG/NCS): Delayed testing (2-3 weeks post-injury) useful for assessing motor unit integrity and denervation. Early studies may show reduced motor evoked potentials after SCI. Most useful for evaluating peripheral causes of cord-like syndromes (e.g., Guillain-Barré) and chronic myelopathy.

• Provocative imaging tests: Upright MRI or standing flexion-extension X-rays for dynamic compression assessment in degenerative myelopathy; special sequences (STIR, phase-sensitive inversion recovery) for demyelination detection.

• Ancillary studies based on etiology: Vitamin B12 level, methylmalonic acid, and homocysteine for B12 deficiency myelopathy; aquaporin-4 and MOG antibodies for demyelinating syndromes; blood cultures and CSF cultures for infectious myelitis; ESR, inflammatory markers for vasculitis; **imaging of

Immediate stabilization (acute traumatic SCI)

• Airway, spinal immobilization, hemodynamic support: high cervical lesions threaten the diaphragm; intubate early for rising PaCO2 or falling vital capacity. AANS/CNS guidelines advise avoiding hypotension and maintaining mean arterial pressure around 85–90 mmHg for roughly the first week to preserve cord perfusion, using vasopressors (norepinephrine) after volume resuscitation.
• Neurogenic shock (hypotension with bradycardia from lost sympathetic outflow) is distinguished from hemorrhagic shock, which is tachycardic; treat with fluids plus vasopressor, and atropine for symptomatic bradycardia.

Etiology-directed first-line therapy

• Corticosteroids: dexamethasone for malignant epidural cord compression (NCCN) and high-dose IV methylprednisolone for acute demyelinating/transverse myelitis; escalate to plasma exchange if steroid-refractory.
• Antibiotics: empiric MRSA coverage with vancomycin plus an antipseudomonal cephalosporin for epidural abscess; per the 2020 IDSA/ASHP consensus vancomycin is dosed to a 24-hour AUC/MIC of 400–600, not to a trough.
• Vitamin B12 repletion: parenteral cyanocobalamin for subacute combined degeneration; treat before, or along with, folate.
• ALS: glutamate-release inhibitor riluzole and free-radical scavenger edaravone, with non-invasive ventilation and multidisciplinary clinic care, which the AAN practice parameters credit with the largest survival benefit.

Definitive/surgical management

• Emergent decompression for cauda equina and conus syndromes, epidural abscess or hematoma with deficit, and unstable fracture; AO Spine guidelines suggest early (within 24 hours) decompression for acute traumatic cervical SCI.
• Laminectomy/fusion for degenerative myelopathy and for stenosis failing NASS-endorsed conservative care (physical therapy, NSAIDs, epidural steroid injection).
• Posterior fossa decompression for Chiari-associated syringomyelia; shunting is reserved for refractory syrinx.

Avoid

• Routine methylprednisolone in acute traumatic SCI — not recommended by AANS/CNS given infection, GI bleeding, and hyperglycemia risk.
• Succinylcholine beyond ~48–72 hours post-injury (receptor upregulation → hyperkalemic arrest) and nitrous oxide in any B12-deficient patient.

Emergencies

• Autonomic dysreflexia (lesions at or above T6): a noxious stimulus below the level — most often bladder distention or fecal impaction — triggers unopposed sympathetic outflow with severe hypertension, while baroreflex-driven vagal tone produces bradycardia, pounding headache, and flushing/sweating above the lesion with pallor below. Sit the patient upright, loosen restrictive clothing, and remove the trigger (catheterize or de-obstruct) before giving a short-acting antihypertensive such as nitrate paste or topical nitroglycerin; risk is hypertensive encephalopathy and intracerebral hemorrhage.
• Respiratory failure: ascending cord edema after cervical injury paralyzes the diaphragm; a falling vital capacity or rising PaCO2, not oxygen saturation, is the signal to intubate.
• Cauda equina/conus decompensation: new urinary retention with an elevated post-void residual and saddle anesthesia mandates emergent MRI and surgery.
• Intrathecal baclofen pump withdrawal: abrupt cessation causes rebound spasticity, fever, rigidity, and rhabdomyolysis mimicking neuroleptic malignant syndrome.

Subacute and chronic disease complications

• Venous thromboembolism: immobility and venous stasis; a swollen calf or unexplained hypoxemia in a patient who cannot report leg pain.
• Neurogenic bladder: detrusor–sphincter dyssynergia raises storage pressures, producing recurrent UTIs, hydronephrosis, and eventual renal failure — historically a leading cause of late mortality.
• Pressure injury and osteomyelitis over sacrum and heels from insensate immobility.
• Spasticity, contractures, and heterotopic ossification (warm swollen joint, elevated alkaline phosphatase).
• Post-traumatic syringomyelia: an ascending cavity months to years later, signaled by new cape-like dissociated sensory loss or rising level of weakness.
• Neuropathic pain, orthostatic hypotension, sublesional osteoporosis with fragility fracture, and depression.

Treatment-related

• Corticosteroids: hyperglycemia, GI bleeding, infection — the harms behind the AANS/CNS position against routine methylprednisolone in traumatic SCI.
• Vancomycin: AUC-related nephrotoxicity.
• Surgery: CSF leak, wound infection, hardware failure, adjacent-segment disease, and C5 palsy after cervical decompression.
• Riluzole: transaminase elevation requiring monitoring.

• **Dissociated sensory loss in a cape distribution is syringomyelia until proven otherwise: the expanding central cavity first interrupts spinothalamic fibers decussating in the anterior white commissure, sparing dorsal columns. Best next step is MRI of the entire neuraxis**, because the tested association is Chiari I malformation.
• Mixed UMN and LMN signs with a completely normal sensory exam = ALS. Fasciculations plus hyperreflexia in the same limb is the giveaway; extraocular movements, bowel/bladder function, and sensation are characteristically spared. Distractor: cervical spondylotic myelopathy, which can mimic it but produces a sensory level and neck pain.
• Subacute combined degeneration hits dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts — a positive Romberg with spastic weakness and paresthesias. Methylmalonic acid and homocysteine are elevated and become abnormal before the B12 level does. Ask about nitrous oxide use, gastric bypass, and vegan diet; giving folate alone corrects the anemia while the myelopathy progresses.
• Lumbar spinal stenosis: pain relieved by flexion (shopping cart sign), worsened by extension and walking downhill. Distinguish from vascular claudication, where pedal pulses are diminished and relief comes from standing still, not from leaning forward.
• Cauda equina syndrome: urinary retention is the most sensitive early finding — check a post-void residual. The correct sequence is emergent MRI then surgical decompression; do not delay imaging for a course of steroids or physical therapy. Contrast with conus medullaris syndrome, which is symmetric with early bowel/bladder involvement.
• Anterior cord syndrome after aortic surgery or dissection: paraplegia with loss of pain/temperature but intact vibration and proprioception, because the posterior spinal arteries are spared.
• Argyll Robertson pupils with dorsal column loss and lancinating pains point to tabes dorsalis, not B12 deficiency — the discriminator examiners plant.
• Do not give routine high-dose methylprednisolone for acute traumatic SCI (AANS/CNS); prioritize decompression and MAP support instead.