Spinal Cord Injury

Spinal cord injury (SCI) is an insult to the spinal cord resulting in a change, either temporary or permanent, in its normal motor, sensory, or autonomic function. The International Standards for Neurological and Functional Classification of Spinal Cord Injury is a widely accepted system describing the level and the extent of injury based on a systematic motor and sensory examination of neurologic function. The following terminology has developed around classification of SCI:

• Tetraplegia (replaced the term quadriplegia) - Injury to the spinal cord in the cervical region with associated loss of muscle strength in all 4 extremities
• Paraplegia - Injury in the spinal cord in the thoracic, lumbar, or sacral segments, including the cauda equina and conus medullaris

SCI can be sustained through different mechanisms with the following 3 common abnormalities leading to tissue damage:

• Destruction from direct trauma
• Compression by bone fragments, hematoma, or disk material
• Ischemia from damage or impingement on the spinal arteries

Spinal shock

Spinal shock is a state of transient physiological (rather than anatomical) reflex depression of cord function below the level of injury with associated loss of all sensorimotor functions. An initial increase in blood pressure is noted due to the release of catecholamines, followed by hypotension. Flaccid paralysis, including of the bowel and bladder, is observed.. These symptoms tend to last several hours to days until the reflex arcs below the level of the injury begin to function again

Motor strengths and sensory testing

The extent of injury is defined by the ASIA Impairment Scale (modified from the Frankel classification), using the following categories:

• A - Complete: No sensory or motor function is preserved in sacral segments S4-S5.
• B - Incomplete: Sensory, but not motor, function is preserved below the neurologic level and extends through sacral segments S4-S5.
• C - Incomplete: Motor function is preserved below the neurologic level, and most key muscles below the neurologic level have muscle grade less than 3.
• D - Incomplete: Motor function is preserved below the neurologic level, and most key muscles below the neurologic level have muscle grade greater than or equal to 3.
• E - Normal: Sensory and motor functions are normal.

Perform rectal examination to check motor function or sensation at the anal mucocutaneous junction. The presence of either is considered sacral-sparing.

Definitions of complete and incomplete SCI are based on the above ASIA definition with sacral-sparing.

• Complete - Absence of sensory and motor functions in the lowest sacral segments
• Incomplete - Preservation of sensory or motor function below the level of injury, including the lowest sacral segments

Sacral-sparing is evidence of the physiologic continuity of spinal cord long tract fibers with the sacral fibers located more at the periphery of the cord. Indication of the presence of sacral fibers is of significance in defining the completeness of the injury and the potential for some motor recovery. This finding tends to be repeated and better defined after the period of spinal shock.

With the ASIA classification system, the terms paraparesis and quadriparesis now have become obsolete. The ASIA classification using the description of the neurologic level of injury is used in defining the type of SCI (eg, C8 ASIA A with zone of partial preservation of pinprick to T2).

Other classifications of SCI include the following:

• Central cord syndrome often is associated with a cervical region injury leading to greater weakness in the upper limbs than in the lower limbs with sacral sensory sparing.
• Brown-Séquard syndrome often is associated with a hemisection lesion of the cord, causing a relatively greater ipsilateral proprioceptive and motor loss with contralateral loss of sensitivity to pain and temperature.

• Anterior cord syndrome often is associated with a lesion causing variable loss of motor function and sensitivity to pain and temperature, while proprioception is preserved.

• The posterior cord syndrome, is the least common of the SCI clinical syndromes. It results from a selective injury to the posterior columns in the spinal cord, leading to a loss of proprioception and vibration sensation below the level of injury.

• Conus medullaris syndrome is associated with injury to the sacral cord and lumbar nerve roots leading to areflexic bladder, bowel, and lower limbs, while the sacral segments occasionally may show preserved reflexes (eg, bulbocavernosus and micturition reflexes).
• Cauda equina syndrome is due to injury to the lumbosacral nerve roots in the spinal canal leading to areflexic bladder, bowel, and lower limbs.

Muscle strengths are graded using the following Medical Research Council (MRC) scale of 0-5.

Muscle strength always should be graded according to maximum strength attained, no matter how briefly that strength is maintained during the examination. The muscles are tested with the patient supine.

The following key muscles are tested in patients with SCI, and the corresponding level of injury is indicated:

• C5 - Elbow flexors (biceps, brachialis)
• C6 - Wrist extensors (extensor carpi radialis longus and brevis)
• C7 - Elbow extensors (triceps)
• C8 - Finger flexors (flexor digitorum profundus) to the middle finger
• T1 - Small finger abductors (abductor digiti minimi)
• L2 - Hip flexors (iliopsoas)
• L3 - Knee extensors (quadriceps)
• L4 - Ankle dorsiflexors (tibialis anterior)
• L5 - Long toe extensors (extensors hallucis longus)
• S1 - Ankle plantar flexors (gastrocnemius, soleus)

Sensory testing is performed at the following levels:

• C2 - Occipital protuberance
• C3 - Supraclavicular fossa
• C4 - Top of the acromioclavicular joint
• C5 - Lateral side of antecubital fossa
• C6 - Thumb
• C7 - Middle finger
• C8 - Little finger
• T1 - Medial side of antecubital fossa
• T2 - Apex of axilla
• T3 - Third intercostal space (IS)
• T4 - 4th IS at nipple line
• T5 - 5th IS (midway between T4 and T6)
• T6 - 6th IS at the level of the xiphisternum
• T7 - 7th IS (midway between T6 and T8)
• T8 - 8th IS (midway between T6 and T10)
• T9 - 9th IS (midway between T8 and T10)
• T10 - 10th IS or umbilicus
• T11 - 11th IS (midway between T10 and T12)
• T12 - Midpoint of inguinal ligament
• L1 - Half the distance between T12 and L2
• L2 - Mid-anterior thigh
• L3 - Medial femoral condyle
• L4 - Medial malleolus
• L5 - Dorsum of the foot at third metatarsophalangeal joint
• S1 - Lateral heel
• S2 - Popliteal fossa in the midline
• S3 - Ischial tuberosity
• S4-5 - Perianal area (taken as one level)

Sensory scoring is for light touch and pinprick, as follows:

• 0 - Absent
• 1 - Impaired or hyperesthesia
• 2 - Intact

A score of zero is given if the patient cannot differentiate between the point of a sharp pin and the dull edge.

Motor level - Determined by the most caudal key muscles that have muscle strength of 3 or above while the segment above is normal (= 5)

Motor index scoring - Using the 0-5 scoring of each key muscle with total points being 25/extremity and a total possible score of 100

Sensory level - Most caudal dermatome with a normal score of 2/2 for both pinprick and light touch

Sensory index scoring - Total score from adding each dermatomal score with possible total score (= 112 each for pinprick and light touch)

Neurologic level of injury - Most caudal level at which both motor and sensory levels are intact, with motor level as defined above and sensory level defined by a sensory score of 2

Zone of partial preservation - This index is used only when the injury is complete. All segments below the neurologic level of injury with preservation of motor or sensory findings

Skeletal level of injury - Level of greatest vertebral damage on radiograph

Lower extremities motor score (LEMS) - Uses the ASIA key muscles in both lower extremities with a total possible score of 50 (ie, maximum score of 5 for each key muscle L2, L3, L4, L5, and S1 per extremity). A LEMS score of 20 or less indicates patients are likely to be limited ambulators. A LEMS of 30 or more suggests that patients are likely to be community ambulators.

SCI due to trauma is not a common condition, but it has a major effect on the injured person's functional, medical, financial, and psychosocial well-being.

The most common causes of SCI include the following:

• Motor vehicle accidents (44.5%) are the major cause of SCI in the United States.
• Falls (18.1%) are most common in persons aged 45 years or older. Older females with osteoporosis have a propensity for vertebral fractures from falls with associated spinal cord injury.
• Violence (16.6%) is the most common cause of SCI in some urban settings in the United States, with a trend showing a slight decrease in violence as a cause of SCI. A recent study showed that an assault causing a penetrating injury tended to be worse than that from a blunt injury.
• Sports injuries (12.7%) cause many cases of SCI. Diving is the sport in which SCI occurs most commonly.

Other causes of SCI include the following:

• Vascular disorders
• Tumors
• Infectious conditions
• Spondylosis
• Iatrogenic injuries, especially after spinal injections and epidural catheter placement
• Vertebral fractures secondary to osteoporosis
• Developmental disorders

The incidence of traumatic SCI in the United States is 30-60 new cases per million population, or 10,000 cases per year in the United States. Some sources cite 8 cases per 10,000 population per year.

Figures on estimated prevalence vary from approximately 183,000 to 230,000 cases in the United States, the equivalent of 700-900 cases per million population.

Sex

The male-to-female ratio of individuals with SCI in the United States is 4:1, ie, males constituting about 80%.

Age

More than 50% of all cases of SCI occur in persons aged 16-30 years. The median age is 26.4 years, while the mean age is 31.8 years and the mode age at injury is 19 years. Traumatic SCI is more common in persons younger than 40 years, while nontraumatic SCI is more common in persons older than 40 years. Greater mortality is reported in the older patients with SCI.

Associated injuries

Other injuries are often associated with traumatic SCI, and these include bone fractures (29.3%), loss of consciousness (17.8%), and traumatic brain injury affecting emotional/cognitive functioning (11.5%).

Level and type of injury

The most common levels of injury on admission are C4, C5 (the most common), and C6, while the level for paraplegia is the thoracolumbar junction (T12). The most common type of injury on admission is ASIA level A.

Injuries by ASIA classification

• Incomplete tetraplegia - 29.5%
• Complete paraplegia - 27.9%
• Incomplete paraplegia - 21.3%
• Complete tetraplegia - 18.5%

The most common neurologic level of injury is C5. In paraplegia, T12 is the most common level.

Life expectancy

Patients aged 20 years at the time of sustaining SCI have life expectancies of approximately 33 years as tetraplegics, 39 years as low tetraplegics, and 44 years as paraplegics. Individuals aged 60 years at the time of injury have a life expectancy of approximately 7 years as tetraplegics, 9 years as low tetraplegics, and 13 years as paraplegics. The annual death rate for patients with acute SCI is 750-1000 deaths per year in the United States.

Leading cause of death

The leading cause of death in patients following SCI is pneumonia and other respiratory conditions, followed by heart disease, subsequent trauma, and septicemia. Among patients with incomplete paraplegia, the leading causes of death among incomplete paraplegics are cancer and suicide (1:1 ratio); among complete paraplegic patients, the leading cause of death is suicide, followed by heart disease. Suicide and alcohol-related deaths are also major causes of death in patients with SCI. The suicide rate is higher among the SCI population who are younger than 25 years.

Functional outcome measures

Several functional-outcome measures are reliable and valid for use in SCI. A common scale for the measurement of functional ability is the Functional Independence Measure (FIM), which uses a 7-point scale to measure 18 items in 6 categories: mobility, locomotion, self-care, continence of the bowel and/or bladder, communication, and social cognition. On the FIM scale, a score of 1 indicates total dependence on a caregiver, and 7 indicates independence. Numbers between 1 and 7 represent different levels of assistance required from a caregiver or assistive device to perform a specific skill.

Additional functional assessment scales are (1) the Quadriplegic Index of Function (QIF), which is designed to detect small but clinically relevant changes in individuals with tetraplegia in 9 categories of activities of daily living (ADL); (2) the Modified Barthel Index (MBI), a 15-item assessment of self-care and mobility skills; (3) the Walking Index for SCI (WISCI), a 21-level scale that has demonstrated validity and responsiveness to change in neurologic/walking function after SCI; (4) the Capabilities of Upper Extremity Instrument (CUE), a 32-item measure for assessing upper-extremity function with tetraplegia; (5) the Spinal Cord Independence Measure (SCIM), which was designed as an alternative to the FIM to assess 16 categories of self-care, mobility, and respiratory and sphincteric function; and (6) the Canadian Occupational Performance Measure (COPM), which is used to assess outcomes in the area of self-care, productivity, and leisure.

C1-C4 OR High Tetraplegia

Individuals with complete high (C1-C4) tetraplegia have little or no movement of upper- and lower-extremity muscles. They have movement of the head and neck and possible shoulder elevation (shrug). Those with an injury at the C4 level have innervation of the diaphragm (the primary muscle for respiratory inspiration). They should not need long-term ventilatory assistance, though it is not uncommon to receive ventilation initially after injury.

Patients with C1-C3 injuries are likely to require long-term mechanical ventilatory support because of the loss of innervation to the diaphragm. These individuals may be candidates for FES of the phrenic nerve (or diaphragm) to reduce their need for mechanical ventilation, if their lower motor innervation to the diaphragm remains intact. Swallowing and phonation functions are preserved.

Individuals with injuries at the C1-C4 level will likely depend on others to help with almost all of their mobility and self-care functions, though they may be able to use a power wheelchair with chin or pneumatic (sip and puff) controls. If their elbow flexion and shoulder movement are suboptimal (muscle grade 2 or 3), a balanced forearm orthosis (BFO) or mobile arm support (MAS) may assist them with feeding and grooming activities. A long bottle or straw can enable and permit independence with drinking.

Patients should be able to communicate with caregivers in the performance of mobility function, self-care, and bladder and/or bowel care. Assistive technologies, such as environmental control units (ECU) may be accessed by using mouth-stick, switch, or voice activation. These devices transmit signals by means of radio waves, infrared light, or ultrasound to facilitate the individual's control of their environment. In this way, they can accomplish tasks such as answering the phone and controlling computers, lights, televisions, and the height of the bed.

C5 tetraplegia

Individuals with C5 tetraplegia have functional use of elbow flexion. With the help of specialized assistive devices (such as wrist or hand orthotics to allow them to hold objects), they can achieve independence with feeding and grooming. It is important to prevent contractures of elbow flexion and forearm supination caused by unopposed biceps activity. Patients with a C5 injury can assist with upper-extremity dressing and bed mobility.

Patients will likely need a power wheelchair with hand controls for most of their mobility, though a manual wheelchair with grip enhancements (rim projections) may be used for short-distance mobility on level surfaces. Patients require assistance for most other self-care (eg, lower-extremity dressing, bathing), for transfer mobility, and for bladder and/or bowel tasks. As with injuries at higher cervical levels than this one, assistive technology (eg, ECUs) can play an important role in maximizing the individual's control of their environment by helping them adjust the height of their bed; answer phones; and use computers, lights, and televisions. Driving a specially modified or adapted van is possible.

C6 tetraplegia

Individuals with C6 tetraplegia have the added function of wrist extension, which permits tenodesis, or passive thumb adduction on the index finger during active wrist extension and thus assists with grasp and release. A wrist-hand orthosis (tenodesis splint) can be used to facilitate these abilities. The patient should avoid overstretching the finger flexors, which limits the tenodesis action.

C6 is the highest level at which patients can have a complete an injury and still independently without the aid of an attendant, though this situation is not common. Individuals with injuries at this level can achieve functional independence with assistive devices in terms of feeding, grooming, bathing, and bed mobility. They can dress their upper body and assist with lower-body dressing. With the use of a slide board, individuals with C6 tetraplegia may become independent in performing transfers from the bed to the chair, though they most often require assistance. Individuals can assist with the bladder and bowel program. Intermittent catheterization for bladder care may be possible with set-up and assistive devices, though it is not common and technically more difficult for women than with men.

Manual wheelchairs with enhancement for gripping the wheel rims may be used for community mobility, though patients may prefer a power chair. Driving an adapted vehicle with adaptations such as a custom lift and hand controls is an option. Patients with C6 injuries can be independent in using a phone, turning pages, and writing and typing (with assistive devices).

C7 tetraplegia

Individuals with C7 tetraplegia have functional ability to extend their elbow, which greatly enhances their mobility and self-care skills. C7 is usually the highest level at which patients might have an injury and still be able to live independently. They may achieve independence in feeding, upper extremity dressing, bathing, bed mobility, transfers (though they may require assistance moving over uneven surfaces), and manual wheelchair propulsion in the community (with exception of going over curbs).

In addition, with the use of assistive devices, patients may also become independent with grooming, lower-extremity dressing and bowel care. Individuals with C7 injury, especially women, may need help with bladder care (eg, intermittent catheterization). Patients might be able to independently drive a car adapted with hand controls or an adapted van. With an injury at this level, patients can be independent, with or without assistive devices, in writing, typing, turning pages, answering the phone, and using the computer.

C8 tetraplegia

Individuals with C8 tetraplegia have functional finger flexion, which improves their independence in terms of hand grasp and release. They can achieve independence with feeding, grooming, upper- and lower-extremity dressing, bathing, bed-mobility transfers, manual wheelchair propulsion, bladder and bowel care, answering the phone, using a computer, typing, and writing. They can drive independently with a car adapted with hand controls or an adapted van.

Thoracic paraplegia

Individuals with T1-T12 paraplegia have innervation and function of all upper-extremity muscles, including hand function. They can achieve functional independence, at the wheelchair level, for all mobility, self-care (including light housekeeping and meal preparation) and bladder and bowel skills. Individuals should receive advanced wheelchair training (moving over uneven surfaces, rough terrain, over ramps and curbs, doing "wheelies," and making transfers from the floor to the wheelchair). Like patients with an injury to the low cervical levels, those with thoracic paraplegia can drive independently by using a car adapted with hand controls or an adapted van.

Individuals with T2-T9 injury have variable trunk control (of the paraspinal and abdominal muscles), and they may be able to stand by using bilateral knee-ankle-foot orthoses (KAFOs) and a walker or crutches. Those with an injury at T10-T12 have better trunk control than those with higher injury, and they may be able to walk household distances independently with KAFOs and assistive devices; they may even attempt to walk up and down stairs. Unfortunately, these maneuvers may require extreme energy expenditure, and many individuals may prefer wheelchair mobility.

Lumbar paraplegia

Individuals with lumbar or sacral paraplegia can achieve functional independence for all mobility, self-care, and bladder and bowel skills. Advanced wheelchair training (as mentioned above) should be undertaken.

Patients with this injury can drive independently by using a car adapted with hand controls. Individuals with an injury at the lumbar level can become functionally independent in terms of household and community ambulation, which is often defined as the unassisted ambulation for distances greater than 150 feet with or without the use of braces and assistive devices (see the section below). Orthotic devices (KAFOs and ankle-foot orthoses [AFOs]) are often prescribed to assist patients with lower-extremity standing and walking. Full- or part-time use of a manual wheelchair is often necessary.

SCI CLINICAL SYNDROMES

The prognosis for enhanced functional outcomes is most favorable for patients with incomplete SCI. Six clinical syndromes, which result from anatomically distinct SCIs, are often discussed.

The first is central cord syndrome (CCS), which is a relatively common cervical incomplete injury characterized by weakness of the upper extremities (especially hands) more than the lower extremities. Individuals with CCS also may have sensory and bladder dysfunction. This syndrome is frequently seen in elderly individuals with degenerative spinal stenosis and is associated with hyperextension injuries. In general, patients with CCS have a favorable prognosis for functional ability for ADLs, bladder and bowel control, and ambulation. Residual upper-extremity weakness may persist and may affect basic self-care, and the patient may need to use assistive devices for ambulation. Favorable prognostic factors are age younger than 50 years (at time of injury), good initial hand or lower-extremity motor score, education, decreased comorbidities, decreased spasticity, and rapid early improvement.

The second is Brown-Sequard syndrome, which is often attributed to spinal cord hemisection. This syndrome is characterized by relative ipsilateral paresis, along with proprioception and/or vibratory loss and contralateral loss of pain or temperature sensation below the level of injury. The prognosis for functional independence of ADLs, bladder and bowel continence, and ambulation is good.

The third is anterior cord syndrome, which is characterized by a variable loss of motor and pinprick sensation, with relatively little effect on proprioception and vibration. Lesions result from damage to the anterior two thirds of the spinal cord while the posterior columns are spared. The prognosis for neurologic recovery is diminished in patients with anterior cord syndrome compared with others; functional outcomes in terms of ADLs and mobility depend on the level of injury.

The fourth, or posterior cord syndrome, is the least common of the SCI clinical syndromes. It results from a selective injury to the posterior columns in the spinal cord, leading to a loss of proprioception and vibration sensation below the level of injury. Motor strength and pain and temperature sensation are relatively spared. Functional outcomes for mobility, self-care and bladder and bowel continence are good, though individuals may require the use of assistive devices (walker, cane) for ambulation.

The fifth is conus medullaris syndrome, which is characterized by injury to the sacral cord and lumbosacral nerve roots. The result is symmetric and often complete saddle anesthesia, bladder and bowel dysfunction, and lower-extremity motor weakness. The functional prognosis for motility and ADLs is good, though bladder or bowel function is less likely than in other conditions, neurologic recovery is limited.

The sixth, or cauda equina syndrome, is characterized by injury to the lumbosacral nerve root injury; therefore, this syndrome is not truly an SCI. The result is saddle anesthesia, bladder and bowel dysfunction, and variable motor weakness of the lower extremity. Cauda equina syndrome is often less complete and less symmetric than conus medullaris injury (see the paragraph above). Because axons of the peripheral nerve root can regenerate (unlike spinal cord axons) and because these injuries are often incomplete, neurologic recovery may continue for many months or years. The functional prognosis for mobility and self-care skills are good, though bladder and bowel continence varies.

Neuroprostheses

Lower-extremity neuroprostheses can enable mobility in individuals with low cervical or thoracic SCI; abilities such as standing, performing transfers, and walking were previously unobtainable with injuries at these levels.

The Parastep device is a commercially available portable FES system in which surface electrodes are placed over the quadriceps, peroneal nerve, and gluteal muscles to stimulate movement and to allow the person to stand and walk. Use of this device is indicated for individuals with neurologic levels at T4-T12. Factors limiting its use may include upper-extremity strength, lower-extremity joint ROM, pain sensation in the lower extremity, ability to tolerate high energy requirements, cardiac disease, clinically significant spasticity, lower motor neuron (LMN) injury of the lower-extremity muscles, and severity of osteoporosis.

Upper-extremity neuroprostheses enhance the potential for upper-extremity movement (especially hand grasp and release) in individuals with C5 or C6 injury. The use of implantable systems, such as the FreeHand system, in combination with surgical reconstruction (see below) provides the greatest opportunity for long-term function. The FreeHand system consists of 8 implanted electrodes and an implanted receiver-stimulator unit. It is controlled by activating an external joystick worn on the patient's chest or shoulder.

Surgical transfers of the brachioradialis to enhance wrist extension in patients with C5 or C6 tetraplegia and/or of the posterior deltoid to triceps to enhance elbow extension in those with C6 tetraplegia as often performed in combination with FES to further improve the person's upper-extremity movement and hand grasp and release. Special considerations include C5 and C6 levels, ASIA classes A or B, LMN innervation of key forearm and hand muscles, neurologic stability, expertise in postsurgical rehabilitation, and patient motivation.

Bladder neuroprostheses have been used in patients with suprasacral SCI to improve their bladder and bowel function. Available devices include the VOCARE system, which applies FES to the sacral nerve roots (which carry parasympathetic efferents). This stimulation causes contraction of the detrusor bladder muscle (for bladder emptying) and facilitates stool transport through the colon. This technique is usually accompanied with posterior rhizotomy, or surgical ablation of the sacral sensory nerve roots, to reduce detrusor hyperreflexia and incontinence. Potential candidates are those who are neurologically stable and who have viable function of the sacral nerve.

Stimulation of respiratory muscles by using implantable phrenic-nerve pacemakers reduces the need for mechanical ventilation in individuals with tetraplegia at C1-3 who would otherwise be ventilator dependent. Potential benefits include increased ease in patient transfers, improved speech, reduced anxiety, improved sense of well-being, reduced need for nursing care, and reduced overall costs. Candidates for phrenic-nerve FES must have an intact phrenic nerve and be free of clinically significant lung disease.

Surgical reconstruction options to improve upper-extremity function in tetraplegia

Surgical reconstruction can improve upper-extremity function in individuals with tetraplegia. Tendons from proximal functioning muscles can be surgically transferred to enhance distal nonfunctioning parts, often improving an individual's motor function by 1 level. For patients with an injury at the C5 level, tendon transfers may enable wrist and elbow extension. For those with injury at the C6 level, tendon transfers may provide for elbow extension and tenodesis to allow them to grasp and release. For those with injury at the C7 level, tendon transfers can restore active grasp and improves hand dexterity.

Careful patient selection and experienced hand surgeons and therapists are essential for successful outcomes. Appropriate candidates for these procedures must be neurologically stable and well motivated to participate in postoperative rehabilitation (immobilization, edema and scar management, mobilization, functional skills training, and strengthening).