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Pathophysiology, causes, and management of non-traumatic spinal injury 

Pathophysiology, causes, and management of non-traumatic spinal injury
Chapter:
Pathophysiology, causes, and management of non-traumatic spinal injury
Author(s):

Oliver Flower

and Matthew Mac Partlin

DOI:
10.1093/med/9780199600830.003.0242
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Key points

  • Non-traumatic spinal cord injury is at least as common as traumatic spinal cord injury and its incidence increases with age.

  • Non-traumatic spinal cord injury has a wide spectrum of aetiologies with varying pathophysiology.

  • A high index of suspicion must be present to avoid delayed diagnosis and treatment.

  • Management of non-traumatic spinal cord injury focuses on diagnosing and treating the precipitating cause, supportive management, and preventing complications.

  • The outcomes of non-traumatic spinal cord injury are similar to those of traumatic spinal cord injury.

Introduction

Non-traumatic spinal cord injury (NTSCI) is the myelopathy caused by a host of conditions other than trauma. While NTSCI shares many clinical and pathological features with traumatic spinal cord injury (TSCI), it has a separate epidemiology and pathophysiology, and its own distinct management elements, largely related to the precipitating causes. Like TSCI, NTSCI has enduring consequences for the individual, their families, and society.

Epidemiology

The incidence of NTSCI equals that of TSCI (10–83/million population/year) [1,2], and in some regions exceeds TSCI [3]‌. Unlike TSCI, the incidence increases with age, predominantly affecting those between 30 and 60, unlike the male preponderance seen in TSCI [3,4].

Causes

A diverse range of aetiologies may cause NTSCI. The most common causes described in case series in developed countries are degenerative disc disease, canal stenosis, tumours, vascular diseases and inflammatory conditions [5,6]. The International Spinal Cord Society (ISCoS) have compiled a validated and comprehensive classification system, which refers to aetiology by cause, time frame of onset, and whether there was an iatrogenic component to the injury [7]‌. The aetiologies are summarized in Table 242.1. Other time-critical diagnoses should be considered with the presentation of acute non-traumatic paraplegia or tetraplegia, such as intracranial vascular or space-occupying lesions, peripheral neuropathies including Guillain–Barré syndrome, disorders of the neuromuscular junction, myopathies, toxidromes, and metabolic disorders, such as hypoglycaemia.

Table 242.1 Classification of the aetiology of NTSCI (condensed)

Acquired abnormalities

Vertebral column degenerative disorders

  • Disc prolapse

  • Ligamentum flavum hypertrophy

  • Ossification of the posterior longitudinal ligament

  • Spinal osteophytosis

  • Spondylolisthesis

  • Spondylosis

  • Spinal stenosis

Metabolic disorders

  • Deficiency (B12, folate, copper, Vit D)

  • Osteoporosis

  • Paget’s disease

  • Osteomalacia

Vascular disorders

  • Haemorrhage (epidural or elsewhere)

  • Vascular malformations

  • Ischaemia (atherosclerosis, aortic dissection, Takayasu’s arteritis, atheromatous emboli, thromboemboli, fibrocartilaginous emboli, decompression sickness, venous infarction, hypotensive-hypoperfusion, fat embolism, idiopathic)

Inflammatory and autoimmune diseases

  • Demyelination

  • Collagen vascular disease (SLE, Sjogren’s, rheumatoid, ankylosing spondylitis, vasculitis)

  • Sarcoidosis

  • Paraneoplastic

  • Arachnoiditis

Radiation related

Radiation myelitis

Toxic

  • Organophosphates

  • Others

Neoplastic

  • Benign (Primary vertebral, extradural, intradural and intrameduallary)

  • Malignant (Neural, primary vertebral, leptomeningeal, secondary, haematological)

Infection

Viral, bacterial, spirochaetal, fungal, parasitic

Miscellaneous

  • Motor neurone disease

  • Syringomyelia

Congenital

Spinal Dysraphism

e.g. Spina bifida occulta

Arnold–Chiari malformation

Types 1–4

Skeletal malformations

e.g. Atlanto-axial dislocation

Other congenital

Congenital syringomyelia

Genetic Disorders

Hereditary spastic paraparesis

Spinocerebellar ataxias

Adrenomyeloneuropathies

Other leukodystrophies

Spinal muscular atrophies

Adapted by permission from Macmillan Publishers Ltd and International Spinal Cord Society: Spinal Cord, New PW and Marshall R, ‘International Spinal Cord Injury Data Sets for non-traumatic spinal cord injury’, 52, pp. 123–32, copyright 2013.

Pathophysiology

Anatomy

The adult spinal cord is approximately 46 cm long and ends around the L1 vertebral level. It is therefore shorter than the length of the vertebral column and spinal cord segmental levels (innervation of myotomes and dermatomes) do not correspond to vertebral levels; for example, the L4 spinal cord segment is at approximately the T11 vertebral level.

The vascular supply to the spinal cord is via the vertebral arteries, which form the single anterior and two posterior spinal arteries. These, in turn, are supplied by segmental radicular arteries that are small branches of the cervical, thoracic and lumbar vessels. The largest of the radicular arteries is the artery of Adamkiewicz, often given off from the T10 level, but varying in position from T7 to L4 [8]‌.

Pathology

Spinal cord injury is usually considered in terms of primary and secondary mechanisms [9]‌. Traumatic spinal cord injury usually consists of a primary compression or contusion or penetration injury followed by secondary injury (often aggravated by hypoxia and hypoperfusion). The primary injury mechanisms in NTSCI include:

  • Compression/contusion: e.g. disc prolapse, tumour, extradural abscess.

  • Inflammation: e.g. infection, transverse myelitis, multiple sclerosis (MSc), radiation.

  • Ischaemia: e.g. aortic dissection, thromboembolic events.

  • Intracellular defects: e.g. metabolic defects, genetic disorders, congenital disorders.

For acquired aetiologies, such as acute disc prolapse, epidural abscess and acute infection, the primary injury involves axonal death, gray matter haemorrhage with necrosis, microglial activation, and release of inflammatory cytokines. The pathology of secondary injury evolves with time. In the initial hours to days, the pathological features are predominantly inflammation, vasogenic, and cytotoxic oedema, haemorrhage, demyelination, neuronal death, and axonal swelling. This may be a protracted process when the aetiology is ongoing (e.g. tumour) or recurrent (e.g. MSc). This is followed in the subsequent weeks by resolution and initial repair, and then over months to years there is gliosis, further demyelination, and potentially syrinx formation related to altered CSF flow. Through preserved axons, adaptive functional plasticity may occur. For genetic and congenital disorders secondary injury phases may not occur.

Management

NTSCI should be considered in any patient presenting with symmetrical weakness or hypoaesthesia at a defined spinal level that continues caudally. Presentation may be highly variable depending on aetiology, the neurological level of injury, and completeness of injury. Specific syndromes also have different presentations (see Table 242.2).

Table 242.2 Cord syndromes

Syndrome

Explanation

Central cord

Weakness and sensory loss greater in the arms than the legs. Typically follows a hyperextension injury with pre-existing canal stenosis. Ischaemia or haematoma in the centre of the cord affect the cervical segments more due to the pattern of lamination of the corticospinal and spinothalamic tracts.

Anterior cord

Loss of motor function, and pain and temperature sensation below the neurological level of injury (NLOI), with preservation of fine touch and proprioception. Less common, typically following interruption of the blood supply to the anterior spinal cord.

Brown–Séquard

Ipsilateral loss of motor, proprioception and fine touch, with contralateral loss of pain and temperature sensation below the NLOI. Usually follows a penetrating SCI damaging only one-half of the spinal cord.

Conus medullaris

Sudden onset, symmetrical paraplegia with mixed upper and lower motor neuron findings, caused by injury at T12/L1.

Cauda equina

Often asymmetrical, gradual onset, lower motor neuron lower limb weakness with saddle area hypoaesthesia or paraesthesia, with bladder and bowel areflexia. Caused by injuries below L1 damaging the sacral nerve roots.

As acquired NTSCI is often an unexpected event, a high index of suspicion may be required for timely diagnosis. An approach of synchronous resuscitation and evaluation should be taken. Resuscitation should be considered in the same manner as TSCI. A careful history and examination considering other differential diagnoses, followed by urgent appropriate investigations is essential.

History

A focused history should be taken, mindful of the potential aetiologies of acquired NTSCI and differential diagnoses. There may be a clear precipitant, such as thoracic abdominal aneurysm surgery, a lumbar puncture in a coagulopathic patient, an air embolism post-diving or previous radiotherapy, making NTSCI a likely diagnosis. Red flag symptoms may point to specific aetiologies, for example, weight loss, night back pain, or a history of cancer may suggest a neoplastic cause. Fever, intravenous drug abuse, recent infections elsewhere, and immunocompromised states make an infective aetiology more likely. Prolonged use of steroids, increasing age, osteoporosis, and mild trauma suggest a degenerative disorder of the vertebral column. A more insidious onset in individuals with pernicious anaemia or nutritional deficiencies may suggest subacute combined degeneration of the cord (SCDC) from Vitamin B12 deficiency. Relapsing and remitting symptoms involving different areas of the CNS is suggestive of MSc.

Examination

This is covered in greater detail in the other chapters involving SCI. A detailed neurological examination is essential, utilizing the globally accepted guidelines of the American Spinal Injury Association [10] documenting the neurological level of injury and the grade of injury, which requires determination of sacral sparing delineating whether the injury is complete or incomplete. Examination may yield clues as to the precipitant, such as a pulsating enlarged aorta with an aneurysmal dissection, features of sepsis for an infectious cause or the other features of a toxidrome such as those seen in organophosphate poisoning

Investigations

Imaging is required to define a lesion’s location, extent, relations and features, and the sequence of imaging will depend on the presentation. Magnetic resonance imaging (MRI) is usually required to adequately demonstrate NTSCI. MRI is more sensitive and specific than computed tomography (CT), can differentiate myelopathy from radiculopathy and better visualizes intervertebral discs and ligaments. If MRI is contraindicated (e.g. older cochlear implants or pacemakers), a CT myelogram (with contrast) may provide additional information to a plain CT. Imaging must be performed urgently in NTSCI as aetiologies, such as epidural abscesses or haematoma may require urgent surgical intervention to prevent further or permanent cord injury. A CT angiogram or digital subtraction angiography may be required to diagnose vascular causes of NTSCI and may offer the potential for concurrent intervention with the latter.

Laboratory studies may help with diagnosis. A leucocytosis, elevated CRP, and positive blood cultures suggest an infective aetiology. Coagulation abnormalities, including thrombocytopenia, support a haemorrhagic cause. A low vitamin B12 level supports a diagnosis of subacute combined degeneration. Elevated serum angiotensin-converting enzyme (ACE), hypercalcaemia, and an elevated alkaline phosphatase are consistent with sarcoidosis. Tumour markers or, in the case of lymphoma, flow cytometry may help diagnose a specific malignancy. Cerebrospinal fluid (CSF) analysis may be helpful, but should not delay urgent imaging. For example, oligoclonal bands help in diagnosing MSc, CSF ACE suggests sarcoid, tumour cells may be found, the typical features of bacterial or viral infections demonstrated, and important differential diagnoses such as Guillain–Barré syndrome excluded. For other specific conditions, further investigations may be indicated, such as evoked potential to diagnose MSc or a positron emission tomography in certain malignancies.

Treatment

The supportive care described in other chapters for TSCI also applies to NTSCI, and these patients should also be managed in specialised spinal injury units [11]. However, the specific cause responsible for the NTSCI must be addressed.

Vertebral column degenerative disorders causing demonstrable cord injury usually require surgical decompression and stabilization. Metabolic causes require correction of the underlying pathology, for example, vitamin B12 deficiency requires immediate and ongoing treatment with parenteral or oral cobalamin. Haemorrhage causing NTSCI from a compressing haematoma requires immediate correction of any coagulopathy and commonly surgical decompression to prevent further cord damage. Ischaemic NTSCI is commonly managed conservatively; however, there may be a role for intravenous thrombolysis, or intra-arterial clot lysis or retrieval in specialist centres, although the effectiveness of such treatments is currently unknown. The use of lumbar CSF drains to improve intra-operative spinal cord perfusion pressure during thoracic aortic surgery has been shown to reduce NTSCI [8,12]. Spinal arteriovenous malformations may be managed with endovascular embolization, either alone or in combination with surgery. Inflammatory conditions, such as transverse myelitis, MSc, or sarcoidosis potentially respond to corticosteroid treatment and other immunomodulatory agents. Early-delayed radiation-induced myelopathy is usually reversible and rarely treated, whereas when it is late-delayed, it is likely to be permanent. There is no evidence to support specific treatment for this, although steroids are often used [13]. The management of the wide variety of spinal tumours differs depending on the type and location of the tumour. Treatment options include chemotherapy, radiotherapy, pre-operative embolization, and surgery. Epidural infections usually require surgical or radiological drainage, as well as appropriate antimicrobial therapy. Congenital causes of NTSCI require surgical intervention once they become symptomatic, for example Arnold–Chiari malformation is commonly managed with occipital and cervical vertebral decompression, spinal dysraphism requires early surgery to prevent urinary incontinence, and symptomatic atlanto-axial dislocation requires cervical decompression and fusion. For genetic causes NTSCI, treatment is supportive and should include genetic counselling and provision of screening for relatives.

Online materials

Reproduced with kind permission from Andy Neill.

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