Description
Computed tomography is used for the evaluation, assessment of severity, and follow-up of diseases of the spine. Its use in the thoracic spine is limited, however, due to the lack of epidural fat in this part of the body. CT myelography improves the contrast severity of CT, but it is also invasive. CT may be used for conditions, e.g., degenerative changes, infection, and immune suppression, when magnetic resonance imaging (MRI) is contraindicated. It may also be used in the evaluation of tumors, cancer, or metastasis in the thoracic spine, and it may be used for preoperative and post-surgical evaluations. CT obtains images from different angles and uses computer processing to show a cross-section of body tissues and organs. CT is fast and is often performed in acute settings. It provides good visualization of cortical bone.

OVERVIEW
*Conservative therapy — This should include a multimodality approach consisting of a combination of active and inactive components. Inactive components, such as rest, ice, heat, modified activities, medical devices, acupuncture and/or stimulators, medications, injections (epidural, facet, bursal, and/or joint, not including trigger point), and diathermy can be utilized. Active modalities may consist of physical therapy, a physician-supervised home exercise program**, regular Osteopathic Manipulative medicine treatments or chiropractic care when considered safe and appropriate.

**Home exercise program (HEP)/therapy — The following elements are required to meet guidelines for completion of conservative therapy:^4,11
•    Information provided on exercise prescription/plan; AND
•    Follow-up with member with documentation provided regarding lack of improvement (failed) after completion of HEP (after suitable 6-week period), or inability to complete HEP due to physical reason, i.e., increased pain, inability to physically perform exercises. (Patient inconvenience or noncompliance without explanation does not constitute “inability to complete” HEP).
•    Dates and duration of failed PT, physician-supervised HEP, or chiropractic treatment should be documented in the original office notes or an addendum to the notes.
 

Table 1: Gait and spine imaging^{59,60,61,62,63,64}

Table 2: CT and Cutaneous Stigmata⁶⁵

Tethered spinal cord syndrome — a neurological disorder caused by tissue attachments that limit the movement of the spinal cord within the spinal column. Although this condition is rare, it can continue undiagnosed into adulthood. The primary cause is myelomeningocele and lipomyelomeningocele; the following are other causes that vary in severity of symptoms and treatment.

• Dermal sinus tract (a rare congenital deformity)
• Diastematomyelia (split spinal cord)
• Lipoma
• Tumor
• Thickened/tight filum terminale
• History of spine trauma/surgery
• Arnold-Chiari Malformation

Sacral dimples  Simple midline dimples are the most commonly encountered dorsal cutaneous stigmata in neonates and indicate low risk for spinal dysraphism. Only atypical dimples are associated with a high risk for spinal dysraphism, particularly those that are large (> 5 mm), high on the back (> 2.5 cm from the anus), or appear in combination with other lesions.⁶⁶ High-risk cutaneous stigmata in neonates include hemangiomas, upraised lesions (i.e., masses, tails, and hairy patches), and multiple cutaneous stigmata (Table 2).

Back pain with cancer history — Bone is the third most common site of metastases after the liver and the lungs, and approximately two-thirds of all osseous metastases occur in the spine.
 
Approximately 60% – 70% of patients with systemic cancer will have spinal metastasis. Radiographic (x-ray) examination should be performed in cases of back pain when a patient has a cancer history, but without known active cancer or a tumor that tends to metastasize to the spine. This can make a diagnosis in many cases. This may occasionally allow for selection of bone scan in lieu of MRI in some cases. When radiographs do not answer the clinical question, then MRI may be appropriate after a consideration of conservative care.

“Neoplasms causing VCF (vertebral compression fractures) include: 1) primary bone neoplasms, such as hemangioma (aggressive type) or giant cell tumors, and tumor-like conditions causing bony and cellular remodeling, such as aneurysmal bone cysts, or Paget’s disease (osteitis deformans), 2) primary malignant neoplasms including but not limited to multiple myeloma and lymphoma and 3) metastatic neoplasms.”²²

Most common spine metastasis involving primary metastasis originate from the following tumors in descending order: breast (21%), lung (19%), prostate (7.5%), renal (5%), gastrointestinal (4.5%), and thyroid (2.5%). While all tumor can seed to the spine, the cancers mentioned above metastasize to the spinal column early in the disease process.³⁷

CT myelogram — Myelography is the instillation of intrathecal contrast media under fluoroscopy. Patients are then imaged with CT to evaluate for spinal canal pathology. Although this technique has diminished greatly due to the advent of MRI due to its non-invasiveness and superior soft-tissue contrast, myelography is still a useful technique for conventional indications, such as spinal stenosis, when MRI is contraindicated, nondiagnostic, or surgeon preference (see guidelines above) brachial plexus injury in neonates, radiation therapy treatment planning, and cerebrospinal fluid (CSF) leak.

Cauda Equina Syndrome

• Symptoms include severe back pain or sciatica along with one or more of the following:
  • Saddle anesthesia - loss of sensation restricted to the area of the buttocks, perineum and inner surfaces of the thighs (areas that would sit on a saddle).
  • Recent bladder/bowel dysfunction
  • Achilles reflex absent on both sides
  • Sexual dysfunction that can come on suddenly
  • Absent anal reflex and bulbocavernosus reflex
• This is a “Red Flag” situation and Lumbar Spine MRI is approvable.

Drop Metastases⁶⁷ — Drop metastases are intradural extramedullary spinal metastases that arise from intracranial lesions. Common examples of intracranial neoplasms that result in drop metastases include pineal tumors, ependymomas, medulloblastomas, germinomas, primitive neuroectodermal tumors (PNET), glioblastomas multiform, anaplastic astrocytomas, oligodendrogliomas and less commonly choroid plexus neoplasms and teratomas.
 
Leptomeningeal carcinomatosis⁶⁸ — Leptomeningeal carcinomatosis is a complication of cancer in which cancerous cells spread to the membranes (meninges) that covers the brain and spinal cord. The most common solid tumors that involve the leptomeninges are breast, lung, melanoma, gastrointestinal, and primary central nervous system tumors.
 

GENERAL INFORMATION
It is an expectation that all patients receive care/services from a licensed clinician. All appropriate supporting documentation, including recent pertinent office visit notes, laboratory data, and results of any special testing must be provided. If applicable: All prior relevant imaging results and the reason that alternative imaging cannot be performed must be included in the documentation submitted.
Where a specific clinical indication is not directly addressed in this guideline, medical necessity determination will be made based on widely accepted standard of care criteria. These criteria are supported by evidence-based or peer-reviewed sources such as medical literature, societal guidelines and state/national recommendations.
 

Policy
INDICATIONS FOR LUMBAR SPINE CT
If there is a combination request* for an overlapping body part, either requested at the same time or sequentially (within the past 3 months) the results of the prior study should be:

• Inconclusive or show a need for additional or follow up imaging evaluation OR
• The office notes should clearly document an indication why overlapping imaging is needed and how it will change management for the patient.
   

(*Unless approvable in the combination section as noted in the guidelines)

For evaluation of neurologic deficits when lumbar spine MRI is contraindicated or inappropriate

• With any of the following new neurological deficits documented on physical exam
  • Extremity muscular weakness (and not likely caused by plexopathy, or peripheral neuropathy)^1,2
  • Pathologic or abnormal reflexes (and not likely caused by plexopathy, or peripheral neuropathy)
  • Absent/decreased sensory changes along a particular lumbar dermatome (nerve distribution): pin prick, touch, vibration, proprioception or temperature (and not likely caused by plexopathy, or peripheral neuropathy)
  • Lower extremity increased muscle tone
  • New onset bowel or bladder dysfunction (e.g., retention or incontinence)- not related to an inherent bowel or bladder process
  • Gait abnormalities (see Table 1 for more details)
  • New onset foot drop (Not related to a peripheral nerve injury, e.g., peroneal nerve)
• Cauda Equina Syndrome as evidence by severe back pain/sciatica along with one of the defined symptoms (see Overview section)

For evaluation of back pain with any of the following when Lumbar Spine MRI is contraindicated^{3,4,5,6,7,8,9,10,11}

• With new or worsening objective neurologic deficits* on exam, as above
• Failure of conservative treatment* for at least six (6) weeks within the last six (6) months
• With progression or worsening of symptoms during the course of conservative treatment*
• With an abnormal electromyography (EMG) or nerve conduction study (if performed) indicating a lumbar radiculopathy. (EMG is not recommended to determine the cause of axial lumbar, thoracic, or cervical spine pain¹²)
• Isolated back pain in pediatric population¹³ — conservative care not required if red flags present. Red flags that prompt imaging include any of the following:
  • Age 5 or younger, OR
  • Constant pain, OR
  • Pain lasting > 4 weeks, OR
  • Abnormal neurologic examination, OR
  • Early morning stiffness and/or gelling, OR
  • Night pain that prevents or disrupts sleep, OR
  • Radicular pain, OR
  • Fever or weight loss or malaise, OR
  • Postural changes (e.g., kyphosis or scoliosis), OR
  •  Limp (or refusal to walk in a younger child)14,15

As part of initial pre-operative/post-operative/procedural evaluation (“CT best examination to assess for hardware complication, extent of fusion and pseudoarthrosis”^11,16 and MRI for cord, nerve root compression, disc pathology, or post-op infection)
Note: If ordered by neurosurgeon or orthopedic surgeon for purposes of surgical planning, a contraindication to MRI is not required.

• For preoperative evaluation/planning
• CT discogram
• Evaluation of post operative pseudoarthrosis after initial X-rays (CT should not be done before 6 months after surgery)
• CSF leak highly suspected and supported by patient history and/or physical exam findings (leak [known or suspected spontaneous (idiopathic) intracranial hypotension (SIH), post lumbar puncture headache, post spinal surgery headache, orthostatic headache, rhinorrhea or otorrhea, or cerebrospinal-venous fistula -preferred exam CT myelogram])¹⁷
• A follow-up study may be needed to help evaluate a patient’s progress after treatment, procedure, intervention, or surgery in the last 6 months. Documentation requires a medical reason that clearly indicates why additional imaging is needed for the type and area(s) requested (routine surveillance post-op not indicated without symptoms)
• Surgical infection as evidenced by signs/symptoms, laboratory, or prior imaging findings
• New or changing neurological deficits or symptoms post-operatively^16,18 — see neurological deficit section above
• When combo requests are submitted (see above statement+) (i.e., MRI and CT of the spine), the office notes should clearly document the need for both studies to be done simultaneously, i.e., the need for both soft tissue and bony anatomy is required¹⁹
  • Combination requests where both lumbar spine CT and MRI lumbar spine are both approvable (not an all-inclusive list):
    • Pathologic or complex fractures
    • Malignant process of spine with both bony and soft tissue involvement
    • Clearly documented indication for bony and soft tissue abnormality where assessment will change management for the patient

For evaluation of trauma or acute injury²⁰

• Presents with any of the following neurological deficits as above
• With progression or worsening of symptoms during the course of conservative treatment*
• History of underlying spinal abnormalities (i.e., ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis) (Both MRI and CT would be approvable)21
• When the patient is clinically unevaluable or there are preliminary imaging findings (X-ray or CT) needing further evaluation

(“MRI and CT provide complementary information. When indicated it is appropriate to perform both examinations”)²⁰

For evaluation of known fracture or new compression fractures with worsening back pain^20,22

• To assess union of a fracture when physical examination, plain radiographs, or prior imaging suggest delayed or non-healing
• To determine the position of fracture fragments
• With history of malignancy (if MRI is contraindicated or cannot be performed)
• With an associated new focal neurologic deficit as above²³
• Prior to a planned surgery/intervention or if the results of the CT will change management

CT myelogram: When MRI cannot be performed/contraindicated/surgeon preference

• When signs and symptoms are inconsistent or not explained by the MRI findings^{24,25,26,27,28}
• Demonstration of the site of a CSF leak (known or suspected spontaneous (idiopathic) intracranial hypotension (SIH), post lumbar puncture headache, post spinal surgery headache, orthostatic headache, rhinorrhea or otorrhea, or cerebrospinal-venous fistula)
• Surgical planning, especially regarding to the nerve roots or evaluation of dural sac

Pars defect (spondylolysis) or spondylolisthesis

• Pars defect (spondylolysis) or spondylolisthesis in adults when Flexion/Extension X-rays show instability
• Clinically suspected Pars defect (spondylolysis) which is not seen on plain films in pediatric population (< 18 yr) (flexion extension instability not required) and imaging would change treatment^29,30,31 when MRI is contraindicated/cannot be performed or surgeon preference

NOTE: Initial imaging (X-ray, or planar bone scan without SPECT; Bone scan with SPECT is superior to MRI and CT in the detection of pars interarticularis pathology including spondylolysis)³²

For evaluation of tumor, cancer, or metastasis with any of the following:
(MRI is usually the preferred study. CT may be needed to further characterize solitary indeterminate lesions seen on MRI)^33,34

• Primary tumor
  • Initial staging primary spinal tumor³⁵
  • Follow-up of known primary cancer of patient undergoing active treatment within the past year or as per surveillance imaging guidance for that cancer
  • Known spinal tumor with new signs or symptoms (e.g., new or increasing nontraumatic pain, physical, laboratory, and/or imaging findings)
  • With an associated new focal neurologic deficit as above²³
• Metastatic tumor
  • With evidence of metastasis on bone scan needing further clarification OR inconclusive findings on a prior imaging exam
  • With an associated new focal neurologic deficit²³
  • Known malignancy with new signs or symptoms (e.g., new or increasing nontraumatic pain, radiculopathy or back pain that occurs at night and wakes the patient from sleep with known active cancer, physical, laboratory, and/or imaging findings) in a tumor that tends to metastasize to the spine^36,37

Further evaluation of indeterminate or questionable findings on prior imaging.

• For initial evaluation of an inconclusive finding on a prior imaging report that requires further clarification. When MRI cannot be performed, is contraindicated, or CT is preferred to characterize the finding³⁶
• One follow-up exam of a prior indeterminate MR/CT finding to ensure no suspicious interval change has occurred. (No further surveillance unless specified as highly suspicious or change was found on last follow-up exam (When MRI cannot be performed, is contraindicated, or CT is preferred to characterize the finding³⁶

Indication for combination studies for the initial pre-therapy staging of cancer, OR active monitoring for recurrence as clinically indicated OR evaluation of suspected metastases

• ≤ 5 concurrent studies to include CT or MRI of any of the following areas as appropriate depending on the cancer: Neck, Abdomen, Pelvis, Chest, Brain, Cervical Spine, Thoracic Spine or Lumbar Spine

For evaluation of known or suspected infection (osteomyelitis), abscess or inflammatory disease when Lumbar Spine MRI is contraindicated^4,38,39,42

• Infection:
  • As evidenced by signs and/or symptoms, laboratory (i.e., abnormal white blood cell count, ESR and/or CRP) or prior imaging findings⁴⁰
  • Follow-up imaging of infection
    • With worsening symptoms/laboratory values (i.e., white blood cell count, ESR/CRP) or radiographic findings⁴¹
• Spondyloarthropathies
  • Ankylosing Spondylitis/Spondyloarthropathies with non-diagnostic or indeterminate X-ray and rheumatology workup

For evaluation of spine abnormalities related to immune system suppression, e.g., HIV, chemotherapy, leukemia, or lymphoma, and lumbar spine MRI is contraindicated³⁸

• As evidenced by signs/symptoms, laboratory, or prior imaging findings

Other Indications for a Lumbar Spine CT when MRI is contraindicated or cannot be performed
(Note- See combination requests, below, for initial advanced imaging assessment and pre-operatively)

• Tethered cord, or spinal dysraphism (known or suspected) based on preliminary imaging, neurological exam, and/or high-risk cutaneous stigmata^42,43,44
• Known anorectal malformations^45,46
• Suspicious sacral dimple (those that are deep, larger than 0.5 cm, located within the superior portion of the gluteal crease or above the gluteal crease, multiple dimples, or associated with other cutaneous markers) (D’Alessandro, 2009) or duplicated or deviated gluteal cleft⁴⁷
  • in patients ≤ 3 months should have ultrasound
• Toe walking in a child when associated with upper motor neuron signs, including hyperreflexia, spasticity; or orthopedic deformity with concern for spinal cord pathology/tethered cord (e.g., pes cavus, clawed toes, leg, or foot length deformity (excluding tight heel cords))
• Known Chiari II (Arnold-Chiari syndrome), III, or IV malformation
• For follow-up/repeat evaluation of Arnold-Chiari I with new signs or symptoms suggesting recurrent spinal cord tethering (For initial diagnosis, see below)
• Suspected neuroinflammatory Conditions/Diseases (e.g., sarcoidosis, Behcet’s)
  • After detailed neurological exam and appropriate initial work up completed

COMBINATION STUDIES WITH LUMBAR SPINE CT WHEN MRI IS CONTRAINDICATED OR CANNOT BE PERFORMED OR SURGEON PREFERENCE

Any combination of Cervical and/or Thoracic and/or Lumbar CTs
Note: These body regions might be evaluated separately or in combination as documented in the clinical notes by physical examination findings (e.g., localization to a particular segment of the spinal cord), patient history, and other available information, including prior imaging.

Exception — Indications for combination studies:^48,49 Are approved indications as noted below and being performed in children who will need anesthesia for the procedure

• Any combination of these studies for:
  • Survey/complete initial assessment of infant/child with congenital scoliosis or juvenile idiopathic scoliosis under the age of 10^50,51,52 (e.g., congenital scoliosis, idiopathic scoliosis, scoliosis with vertebral anomalies)
  • In the presence of neurological deficit, progressive spinal deformity, or for preoperative planning⁵³
  • Back pain with known vertebral anomalies (hemivertebrae, hypoplasia, agenesis, butterfly, segmentation defect, bars, or congenital wedging) in a child on preliminary imaging
  • Scoliosis with any of the following:⁵⁴
    • Progressive spinal deformity;
    • Neurologic deficit (new or unexplained);
    • Early onset;
    • Atypical curve (e.g., short segment, > 30’ kyphosis, left thoracic curve,
    • associated organ anomalies);
    • Pre-operative planning; OR
    • When office notes clearly document how imaging will change management
• Arnold-Chiari malformations^55,56
  • Arnold-Chiari I
    • For evaluation of spinal abnormalities associated with initial diagnosis of Arnold-Chiari Malformation. (C/T/L spine due to association with tethered cord and syringomyelia), and initial imaging has not been completed^44,50
  • Arnold-Chiari II – IV — For initial evaluation and follow-up as appropriate
    • Usually associated with open and closed spinal dysraphism, particularly meningomyelocele)
• Tethered cord, or spinal dysraphism (known or suspected) based on preliminary imaging, neurological exam, and/or high-risk cutaneous stigmata,^42,43,44 when anesthesia required for imaging⁵⁷ (e.g., meningomyelocele, lipomeningomyelocele, diastematomyelia, fatty/thickened filum terminale, and other spinal cord malformations)
• Oncological Applications (e.g., primary nervous system, metastatic)
  • Drop metastasis from brain or spine (imaging also includes brain; CT spine imaging in this scenario is usually CT myelogram) — see Overview
  • Suspected leptomeningeal carcinomatosis (LC)⁵⁸ — see Overview
  • Any combination of these for spinal survey in patient with metastases
  • Tumor evaluation and monitoring in neurocutaneous syndromes
• CSF leak highly suspected and supported by patient history and/or physical exam findings (leak (known or suspected spontaneous (idiopathic) intracranial hypotension (SIH), post lumbar puncture headache, post spinal surgery headache, orthostatic headache, rhinorrhea or otorrhea, or cerebrospinal-venous fistula -preferred exam CT myelogram))¹⁷
• CT myelogram when meets above guidelines and MRI is contraindicated or for surgical planning
• Post-procedure (discogram) CT
   

References   

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive. 

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community, Blue Cross Blue Shield Association technology assessment program (TEC) and other nonaffiliated technology evaluation centers, reference to federal regulations, other plan medical policies, and accredited national guidelines.

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