Definition

Lumbosacral spinal cord injury (SCI) refers to impairment or loss of motor or sensory function in the lumbar or sacral segments of the spinal cord, secondary to damage of neural elements within the spinal canal [1]. With this level of injury, arm and trunk functions are spared, but the legs and pelvic organs are involved.

The terms lumbosacral SCI and paraplegia are also used in referring to conus medullaris and cauda equina injuries but not to impaired sensorimotor function due to neural involvement outside the spinal canal (as in lumbosacral plexus lesions or injury to peripheral nerves). Conus medullaris syndrome results from an injury to the sacral spinal cord (conus) and lumbar nerve roots within the spinal canal. Cauda equina syndrome refers to injury to the lumbosacral nerve roots within the neural canal.

Lumbosacral injuries account for about 11% of SCI cases in the national Spinal Cord Injury Model Systems database [2]. The most common causes of injury include motor vehicle crashes, falls, acts of violence, and recreational sporting activities [3,4]. There is an association between level of injury and cause of injury, and acts of violence are more often associated with paraplegia than with cervical injury and tetraplegia [2].

Neurologic versus Skeletal Level of Injury

Lumbosacral SCI refers to the neurologic level of injury, which is different from the skeletal level of injury. Because of the discrepancy between the lengths of the spinal cord and the vertebral column, the L1-L5 lumbar spinal cord segments are typically located at the T11-T12 vertebral level, and the S1-S5 sacral spinal cord segments are at the L1 vertebral level. The spinal cord ends between T12 and L2 (most often at L1 vertebra), and injury within the neural canal below that bone level involves the cauda equina. Lesions at the level of the lowermost thoracic and first lumbar vertebrae may result in mixed cauda equina and conus medullaris lesions (Fig. 157.1).

Symptoms

Lumbosacral SCI may be manifested with weakness in the lower extremities, numbness and tingling, bladder and bowel disturbances (urinary retention, constipation, bladder or bowel incontinence), impotence, back pain, and burning perianal or lower extremity pain.

In the outpatient setting, patients may also present with secondary conditions and associated problems, such as urinary tract infections or pressure ulcers. Patients with SCI may have vague, atypical, or nonspecific symptoms. Classic symptoms of urinary tract infection, such as urinary frequency, urgency, and dysuria, may be absent, and patients may present instead with an increased frequency of spontaneous voiding or increased muscle spasms [5]. Fever and malaise may be indicative of a urinary tract infection but can also be due to other infections (such as osteomyelitis underlying a pressure ulcer) or noninfectious causes, such as osteoporotic long bone fracture, deep venous thrombosis, heterotopic ossification, or drug fever (e.g., due to antibiotics). Unilateral leg swelling may be the only presentation of osteoporotic lower limb fractures but could also be due to deep venous thrombosis, heterotopic ossification, hematoma, or cellulitis in the setting of SCI [6].

Pain is a common symptom in people with SCI, and some studies suggest that pain prevalence may be even higher with paraplegia than with cervical injury and tetraplegia [7,8]. A comprehensive history of pain characteristics is needed to accurately determine the underlying cause, which may be nociceptive, neuropathic, or a combination of both.

New weakness or sensory deficits in the upper extremities may indicate post-traumatic syringomyelia extending into the cervical spinal cord or a peripheral nerve entrapment, such as the median nerve at the carpal tunnel or ulnar nerve at the elbow [9]. Patients with chronic SCI who present with extension or worsening of lower extremity weakness or numbness may have post-traumatic syringomyelia or spinal cord or nerve root compression due to progressive spinal deformity or instability.

Rectal bleeding is often caused by hemorrhoids but may be a manifestation of more serious disease, such as colorectal cancer [10]. Similarly, hematuria may be due to urinary tract infection, stones, or catheter-induced trauma, but bladder cancer should be considered in the differential diagnosis, especially in smokers and those with chronic indwelling bladder catheters [5].

Mood disturbances are common in SCI [11]. Depression may be manifested with somatic symptoms such as appetite change and sleep disturbance, although symptoms like loss of energy may be difficult to interpret in the setting of SCI [11,12]. Because many medical diseases may produce similar somatic symptoms, it is helpful to inquire about specific symptoms typically associated with depression, such as suicidal thoughts, dysphoria, and feelings of hopelessness and worthlessness. Early morning awakening is suggestive of primary depression, and fatigue caused by depression is often worse in the morning.

There may be reduced lumbar lordosis due to muscle spasm from pain. Spine fractures may result in deformity, and palpation may reveal areas of tenderness.

Evidence of Concurrent Injuries

Concurrent injuries, including head injury, extremity fractures, and abdominal visceral injury, may accompany lumbosacral SCI and should be considered during diagnostic examination.

Neurologic Examination

Neurologic examination is conducted in accordance with the International Standards for Neurological and Functional Classification of Spinal Cord Injury published by the American Spinal Injury Association [1]. The neurologic findings may sometimes be subtle (e.g., limited to perineal anesthesia or urinary retention) and can be missed in the setting of acute trauma with routine placement of an indwelling catheter or drug-induced sedation, unless they are carefully considered [13]. The neurologic examination should be repeated at regular intervals to monitor for improvement or deterioration [14].

Sensory Examination

The required portion of the sensory examination is completed through testing of key points in each dermatome on the right and left sides of the body (Table 157.1) for pinprick (tested with a disposable safety pin) and light touch sensation (tested with cotton). Pinprick and light touch sensation are separately scored at each key point on a 3-point scale: 0, absent; 1, impaired; and 2, normal. In testing for pinprick sensation, inability to distinguish dull from sharp sensation is graded 0.

Motor Examination

Muscle strength is graded on a 6-point scale of 0 to 5; 0 is no contraction and 5 is normal strength. For the lumbosacral myotomes, five key muscle groups are tested bilaterally (Table 157.2).

Neurologic Rectal Examination

Neurologic rectal examination includes determination of deep anal sensation and testing for voluntary contraction of the external anal sphincter around the examiner’s finger (graded as present or absent). If there is voluntary contraction of the anal sphincter, the patient has a motor incomplete injury.

Additional Neurologic Examination