Definition
- Neurological deterioration ascending ≥4 vertebral levels within weeks after SCI, unrelated to mechanical instability or syrinx.
General
- Distinguishes SPAM from acute (hours–days) and late (≥2 months) deterioration after SCI.
- A subacute syndrome with characteristic ascending neurological level and no mechanical or syrinx‑related cause.
- History
- First described by Frankel in 1969 in patients with neurological levels ascending ≥4 segments after thoracolumbar fracture‑dislocation.
- Largely unrecognised for ~30 years until a 1999 case with MRI‑confirmed SPAM after T11/12 fracture‑dislocation.
- More cases reported over the last two decades with increasing MRI use, clarifying clinical and imaging patterns.
Numbers
- Reports SPAM as rare
- 33 reported patients from 13 published articles.
- Estimated incidence of SPAM among SCI ranges from 0.42% to 1%.
- Poor prognosis
- Mortality ~9–10%,
- Substantial morbidity and prolonged hospitalisation, often requiring ventilation.
- Majority are young and middle‑aged patients;
- about 90% are under 50 years.
- Marked male predominance with approximately 5:1 male:female ratio.
- Over one‑third of cases have initial injury at the thoracolumbar junction.
- Initial injuries are usually fracture‑dislocations or burst fractures with complete paraplegia or tetraplegia.
- Most patients lack major associated injuries apart from SCI itself.
Pathophysiology
General
- Multiple hypotheses proposed: altered CSF circulation, venous thrombosis/congestive ischaemia, hypotensive ischaemia, GAA thrombosis, infection, apoptosis, inflammatory/secondary injury, arterial thrombosis, meningitis/myelitis.
- No single mechanism adequately explains all clinical and pathological findings.
Alteration of CSF circulation
- SCI can acutely elevate CSF pressure, with swollen cord occluding the subarachnoid space and only partial relief from epidural decompression.
- Postoperative MRI often shows the cord filling the subarachnoid space despite decompression.
- Proposed that intramedullary haemorrhage, oedema and debris obstruct spinal canal drainage, causing presyrinx‑like state and cord expansion.
- Obstructed CSF flow may lead to prolonged T2 signal change, cord oedema, and progressive myelomalacia
- Some reversibility with decompression, duraplasty or cordectomy has been reported.
- Persistent intrathecal pressure elevation may ultimately cause intramedullary ischaemia and irreversible deterioration.
- Temporal pattern of SPAM fits delayed development of arachnoid tethering and CSF flow imbalance.
Artery of Adamkiewicz thrombosis
- Suggested because many injuries occur at thoracolumbar levels where the Artery of Adamkiewicz commonly enters.
- Arguments against:
- Expected abrupt rather than progressive course
- Preservation of posterior column function
- Negative spinal angiography
- Central (not anterior) MRI involvement
- Lack of thromboembolus on autopsy
Venous thrombosis and congestive ischaemia
- SCI often reverses normal haemodynamic gradient, increasing vena caval pressure and impairing valveless paravertebral venous drainage.
- Venous congestion may preferentially affect central/posterior cord, consistent with MRI and autopsy findings.
- Central involvement could reflect grey matter sensitivity to ischaemia; ascending course may mirror progression of venous thrombosis.
- Some cases worsened in sitting position or with bracing, supporting a role for increased venous pressure.
- However, venous pressure abnormalities are common after SCI whereas SPAM is rare, indicating this cannot be the sole mechanism.
Hypotensive ischaemia
- Sustained hypotension in SCI, especially with fracture‑dislocations, associated with delayed neurological deterioration.
- Orthostatic changes (e.g. early sitting, increased intra‑abdominal pressure) may reduce spinal perfusion and exacerbate ischaemia.
- Some patients developed symptoms when first mobilised upright.
- Does not fully account for progressive and ascending pattern without repeated or sustained hypotensive episodes; many SPAM patients are haemodynamically stable.
Infection
- Supportive observations include subacute temporal course, pyrexia and poor recovery, resembling transverse myelitis.
- Some data link early post‑SCI leucocytosis with deterioration.
- Steroid‑responsive cases and CSF/autopsy studies showed no infectious cause, arguing against infection as the primary mechanism.
Apoptosis
- Apoptosis of oligodendrocytes and remote apoptotic changes from initial injury site suggest a role in progression.
- Apoptosis likely contributes to myelin degeneration and axonal dysfunction.
- Authors consider apoptosis more a downstream process than the initiating event, given partial clinical and radiological recovery in some cases.
Other hypotheses
- Inflammatory and secondary injury processes considered but are typically most intense immediately post‑injury and are common, whereas SPAM is delayed and rare.
- These mechanisms alone are considered unconvincing as primary explanations.
Risk factors
- Complete SCI, especially with fracture‑dislocation or burst fracture.
- Injury at thoracolumbar junction.
- Asymptomatic chronic low blood pressure.
- Early postoperative orthostatic mobilisation.
- Non‑surgical management of the initial SCI.
- Surgical decompression and rigid internal fixation associated with lower incidence of neurological deterioration in SCI cohorts.
Clinical evaluation
- SPAM typically follows a latent period of several days to weeks of clinical stability.
- Many patients report new pain (arms, shoulders, scapula, neck, chest, trunk) preceding motor decline.
- Other prodromal symptoms include paraesthesia, upper limb weakness, and ascending trunk numbness.
- Fever from low‑grade to high can accompany deterioration; occasionally MRI features of SPAM appear without clear clinical change.
- Neurological deficits may partially improve but rarely return to pre‑deterioration level.
- In severe cases, rapid progression to complete tetraplegia and respiratory compromise can occur, sometimes within hours to days, requiring ventilation.
- Pain may resolve spontaneously over days in some patients.
- Diagnosis relies on careful serial neurological examination including motor, sensory, reflex and perineal assessment, with level‑specific signs (e.g. dysaesthesia in trunk/arms/hands, ascending paraplegic level, upper limb weakness, absent upper‑limb reflexes).
Investigation
Radiological evaluation
MRI
- MRI is considered the diagnostic gold standard for SPAM.
- Typical findings: central high T2 signal extending at least four segments above initial injury, sometimes up to 19 levels and occasionally into the medulla.
- Lesion usually shows tapered superior extent, minimal heterogeneous T1 signal, mild–moderate cord expansion, preserved peripheral cord rim, and absence of syrinx.
- Diffuse intrathecal haemorrhage may be present in some cases.
- MRI changes may not strictly parallel clinical course and can appear without overt neurological deterioration.
- Over time, MRI often improves, then later shows cord atrophy and myelomalacia with sharply circumscribed central/posterior high T2 and low T1 signal.
- MRI‑compatible instrumentation is recommended to avoid artefact at the initial injury site.
- Gadolinium does not substantially change diagnostic appearance.
Other modalities
- CT myelography can show cord swelling above the initial injured level without extrinsic compression.
- Conventional myelography may reveal diffuse cord swelling spanning a few segments around the fracture and a block at fracture level, but no significant compression above.
- Electrophysiology (EMG, motor‑evoked potentials) can identify denervation in muscles innervated by affected segments.
- Selective spinal angiography generally shows normal arterial anatomy without thrombosis or vascular malformation.
- Other imaging (ultrasound of neck/vertebral vessels, chest radiograph, lung scan, brain imaging, dynamic cervical X‑rays) is typically unremarkable early in deterioration.
CSF examination
- Lumbar puncture often demonstrates a complete or partial block below the injury, with no block at the injury level.
- CSF commonly shows elevated protein and neutrophil counts.
- Grossly, CSF may be turbid (“dishwater‑like”) with visible debris.
- Cultures are negative for bacteria, parasites, viruses and tuberculosis.
Management
General
- No definitive or evidence‑based therapy exists due to rarity and uncertain pathogenesis.
- Management is challenging and prognosis generally poor despite interventions.
Supportive treatment
- Emphasises strict blood pressure monitoring and maintenance in the acute SCI phase.
- Requires close surveillance of neurological status and sensory level for early detection of deterioration.
- Recommends bed rest to minimise orthostatic hypotension.
- Oxygen supplementation and mechanical ventilation are indicated when respiratory compromise develops.
Medication therapy
- Reported conservative therapies include anticoagulants, steroids, broad‑spectrum antibiotics and osmotic agents.
- Anti‑apoptotic pharmacotherapy is suggested conceptually but has not been reported in clinical use for SPAM.
- Mild neurological improvement over time is common, but no medication has shown clear benefit in functional outcome.
- There is no consensus on optimal drug choice, dosage or duration, and deterioration has occurred despite steroid use.
Operative therapy
- Surgical approaches aim to reduce CSF pressure and improve CSF flow in line with the CSF‑alteration hypothesis.
- Techniques include laminectomy for epidural decompression, untethering with expansive duraplasty, and cordectomy combined with untethering.
- These operations have been associated with halting progression and/or some neurological improvement in individual cases.
- Laminectomy can relieve CSF block at injury; untethering and cordectomy may facilitate interstitial fluid drainage when the central canal is compromised.
Prognosis
- SPAM carries a poor neurological prognosis overall.
- Some patients achieve slight improvement of one or more levels below the peak level of deterioration.
- Mortality is around 9–10%, and survivors frequently experience substantial disability and prolonged hospital stays.