Anterior spinal cord syndrome of unknown etiology

Abstract

A spinal cord injury encompasses a physical insult to the spinal cord. In the case of anterior spinal cord syndrome, the insult is a vascular lesion at the anterior spinal artery. We present the cases of two 13-year-old boys with anterior spinal cord syndrome, along with a review of the anatomy and vasculature of the spinal cord and an explanation of how a lesion in the cord corresponds to anterior spinal cord syndrome.

Anterior spinal cord syndrome (ACS) is a lesion affecting the anterior two-thirds of the spinal cord with loss of motor control below the lesion with intact crude sensation (1, 2). A true ACS results from a vascular lesion at the anterior spinal artery (ASA) resulting in ischemic injury to the respective area of the spinal cord. Patients present with complete motor defects below the lesion, along with sensory defects affecting pain and temperature sensation. The intensity of the sensory deficits depends on the level of involvement in the spinal cord. Herein we present the cases of ACS in two 13-year-old boys.

CASE 1

At the end of a class period, a 13-year-old boy was unable to get up from his chair. He was taken to the community hospital and found to have bilateral lower-extremity paralysis, without any signs or symptoms of infection. Computed tomography of the head and laboratory results were within normal limits, and he was transferred to a tertiary care pediatric hospital. Examination demonstrated absent deep tendon reflexes and 0/5 muscle strength in his bilateral lower extremities with a sensory level of T8. He had intact proprioception and vibration, with absent pain and temperature sensation. Diagnostic studies, including hematological workups and blood and spinal fluid cultures, were all negative except for elevated Factor VIII, Protein S, and Protein C, which was attributed to an acute inflammatory reaction. Magnetic resonance imaging (MRI) of the spine showed increased T2 signal intensity in the anterior aspect of the spinal cord from approximately the T5 to T6 level through the mid-T8 level (Figure 1). The patient was treated with a tapering schedule of high-dose corticosteroids. Upon stabilization, he was transferred to a pediatric specialty hospital for further rehabilitation and training.

Figure 1.

MRI in case 1. An axial image shows increased T2 signal intensity in the anterior aspect of the spinal cord at the T6 level.

On admission, he had 0/5 muscle strength and absent deep tendon reflexes in his lower extremities. His sensation to light touch and pinprick was altered below T5 with an absence of sensation around the perianal region. On the American Spinal Injury Association Impairment Scale (AIS), he was diagnosed as T5 grade C.

Over the course of his rehabilitation stay, the patient regained full control of his bladder function along with some lower-extremity muscle strength and was ambulating with moderate to maximum assistance with a walker. His sensation to light touch and pinprick remained abnormal with inconsistent sensation to pinprick at the S2 and S3 levels. The inconsistency was due to the patient's comprehension of directions and poor attention to the lengthy evaluation process. Although the patient had pressure sensation on digital rectal exam, he lacked voluntary anal contraction and had an absent bulbocavernosus reflex.

His rehabilitation team consisted of physical therapy, occupational therapy, and psychology support under the supervision of a health care professional trained in caring for patients with a spinal cord injury. The patient and his family were educated on his diagnosis and associated complications. Based on his diagnosis and home evaluations, necessary home modifications (e.g., a ramp to get into the house) were recommended and completed prior to discharge. He was sent home with a loaner wheelchair and continued subcutaneous Lovenox for 3 months, with subsequent follow-ups in the outpatient clinic.

CASE 2

A 13-year-old healthy boy heard a “pop” in his lower back while doing a “burpee” in his physical education class. He immediately felt pain in his back with tingling and shaking in his legs. While walking to the nurse's office after the class, the patient fell and was unable to get up. He experienced loss of sensation below his waist, an inability to move his legs, and excruciating back pain. Examination in the emergency room revealed paraplegia with intact sensation and strength in both his arms and showed signs of bladder retention. Acute hematological and viral workups were negative. MRI of the spine was suggestive of an ischemic or demyelinating process with no imaging findings of arterial venous malformation or dural arteriovenous fistula on diffusion-weighted imaging (Figure 2). The patient was treated with 5 days of intravenous corticosteroids with no return of function and then was admitted to a pediatric specialty hospital for rehabilitation therapy.

Figure 2.

MRI in case 2. (a) An axial image shows an increased T2 signal and edema in the cord at T8. (b) A sagittal image shows increased signal running caudally from T6 to T11.

During his inpatient rehabilitation stay, he continued to lose sensation to light touch. The follow-up MRI of the spine was consistent with myelomalacia (Figure 3), prompting transfer back to acute care for further management. He was treated with five sessions of plasmapheresis with no improvement of symptoms and with negative workup. The patient then returned to a pediatric specialty hospital for completion of therapy, at which point he was diagnosed as T11 AIS A. He failed to make any improvements in his motor or sensory function for his remaining rehabilitation stay.

Figure 3.

Follow-up MRI of the spine in case 2. A sagittal view shows volume loss of cord tissue with an irregular cord margin and adhesions.

The patient and his family received education about his new diagnosis and any associated complications that could occur. The family was trained in management of neuropathic pain and neurogenic skin, bowel, and bladder. The patient was discharged home at the maximum assist level for all activities of daily living. He received appropriate adaptive equipment and had outpatient follow-up scheduled.

DISCUSSION

The spinal cord is an extension of the brain that extends down to L1–L2. It is composed of motor neurons, interneurons, and axons traveling the whole length of the spinal cord. Fasciculus gracilis and fasciculus cuneatus, located in the posterior aspect of the cord, carry sensory information regarding light touch and vibration. The spinothalamic and spinocerebellar tract located in the anterolateral aspect of the spinal cord carry information regarding pain, temperature, and proprioception from the extremities to the brain. The corticospinal and corticobulbar tract located on the anteromedial portion of the spinal cord carry motor information from the brain to the extremities (3).

Blood supply to the spinal cord is provided by one ASA and two posterior spinal arteries, all three of which originate from the vertebral arteries. The posterior spinal arteries occasionally originate from the posterior inferior cerebellar artery. The spinal arteries are supplemented by medullary arteries from the vertebral artery in the cervical region and from intercostal arteries in the thoracic and lumbar region. The artery of Adamkiewicz is a major artery that feeds the spinal arteries in the lower half of the spinal cord and joins the anterior spinal artery at T5. The ASA provides blood supply to the anterior two-thirds of the spinal cord, while the two posterior spinal arteries provide blood supply to the posterior one-third of the spinal cord (3, 4).

ACS results from a loss of blood supply to the anterior two-thirds of the spinal cord, due to a thrombotic or embolic cause affecting the ASA (5, 6). Most of the reported cases are secondary to postoperative complications in adults, such as the repair of an abdominal aortic aneurysm (5), and the patient presents with a complete loss of motor function below the level of injury with altered or no loss in sensation (4).

Depending on the level of injury, the patient is at risk for autonomic dysreflexia, sexual dysfunction, neuropathic pain, gait impairment, and neurogenic bowel, bladder, and skin. The corticospinal and corticobulbar tracts are supplied by the ASA and are affected in ACS. The spinothalamic and spinocerebellar tract can be referred to as the watershed area because of dual vascular supply and location (1, 5). The sensation is altered depending on the level of involvement at the watershed area. In ACS, sensation to light touch is intact since the blood supply to fasciculus gracilis and cuneatus is from the posterior spinal artery.

Successful long-term management of spinal cord injury after the initial hospital stay is dependent upon effective and comprehensive rehabilitation of the patients prior to discharge home. Patients require intensive physical therapy, occupational therapy, and psychological support under the supervision of a health care professional trained in caring for patients with spinal cord injuries. Patients and families should be educated on their new diagnosis and associated complications. Patients need to be evaluated for medical equipment to help with mobility and activities of daily living depending on their level of injury. Social work assistance helps address any challenges concerning patient and family that impact discharge goals. Patients and families need to be trained in caring for and assisting with patient needs. A home visit by a trained therapist will be beneficial in identifying the home modifications needed based on the patient's level of injury. The recommended home modifications should ideally be completed prior to discharge. Furthermore, the patient and family should be provided information about local support groups for community integration. Finally, patients will require long-term physiatric care for the management of spasticity, neuropathic pain, mobility impairment, and neurogenic skin, bowel, and bladder.

Our patients were initially evaluated for transverse myelitis and were eventually diagnosed with ACS due to a lack of serological and imaging studies. We propose considering a spinal cord angiogram or magnetic resonance angiography of the spinal cord in patients presenting with motor and sensory symptoms to evaluate for a true ischemic insult.