Description
Computed tomography’s use of thin sections with multi-planar reconstruction (e.g., axial, coronal, and sagittal planes), along with its three-dimensional rendering, permits thorough diagnosis and management of ocular and orbital disorders. Brain CT is often ordered along with CT of the orbit for head injury with orbital trauma. MRI Orbits is preferred over CT Orbits except in the case of orbital trauma, infection, or bone abnormalities.

Temporal bone, mastoid, and internal auditory canal computed tomography (CT) is a unique study performed for problems, such as conductive hearing loss, chronic otitis media, mastoiditis, cholesteatoma, congenital hearing loss and cochlear implants. It is a modality of choice because it provides 3D positional information and offers a high degree of anatomic detail. It is rarely used for evaluation of VIIth or VIIIth nerve tumors.

Policy
INDICATIONS FOR ORBIT CT

Note: CT is preferred for visualizing bony detail and calcifications. MRI is superior for the evaluation of the visual pathways, globe, and soft tissues is considered MEDICALLY NECESSARY for the following indications:

• Abnormal external or direct eye exam¹:
  • Exophthalmos (proptosis) or enophthalmos
  • Ophthalmoplegia with concern for orbital pathology³
  • Unilateral optic disk swelling if MRI is contraindicated or cannot be performed^4-6
  • Documented visual defect if MRI is contraindicated or cannot be performed^7-10
    • Unilateral or with abnormal optic disc(s) (i.e., optic disc blurring, edema, or pallor); AND
    • Not explained by an underlying diagnosis, glaucoma, or macular degeneration
• Optic Neuritis if MRI is contraindicated or cannot be performed
  • If atypical presentation (bilateral, absence of pain, optic nerve hemorrhages, severe visual impairment, lack of response to steroids, poor recovery or recurrence)^11-14
  • If needed to confirm optic neuritis and rule out compressive lesions
• Orbital trauma
  • Physical findings of direct eye injury
  • Suspected orbital trauma with indeterminate X-ray
  • For further evaluation of a fracture seen on X-ray for treatment or surgical planning
• Orbital or ocular mass/tumor, suspected, or known^{1, 7}
• Clinical suspicion of orbital infection^{15, 16}
• Clinical suspicion of osteomyelitis^{17, 18}
  • Direct visualization of bony deformity OR
  • Abnormal X-rays
• Clinical suspicion of Orbital Inflammatory Disease (e.g., eye pain and restricted eye movement with suspected orbital pseudotumor) if MRI is contraindicated or cannot be performed¹⁹
• Congenital orbital anomalies²⁰
• Complex strabismus (with ophthalmoplegia or ophthalmoparesis) to aid in diagnosis, treatment and/or surgical planning^21-23

Combination Studies with Orbit CT

• Brain CT/Orbit CT if MRI is contraindicated or cannot be performed
  • Optic neuropathy or unilateral optic disk swelling of unclear etiology to distinguish between a compressive lesion of the optic nerve, optic neuritis, ischemic optic neuropathy (arteritic or non-arteritic), central retinal vein occlusion, or optic nerve infiltrative disorders²⁴
  • Bilateral optic disk swelling (papilledema) with vision loss⁵
  • Approved indications as noted above and being performed in high-risk populations and will need anesthesia for the procedure and there is a suspicion of concurrent intracranial pathology²⁵

INDICATIONS FOR SELLA CT²⁶
When MRI is contraindicated or cannot be performed^{27, 28}

• For further evaluation of known sellar and parasellar masses
• Suspected pituitary gland disorder²⁹ based on any of the following:
  • Documented visual field defect suggesting compression of the optic chiasm; OR
  • Laboratory findings suggesting pituitary dysfunction³⁰; OR
  • Pituitary apoplexy with sudden onset of neurological and hormonal symptoms; OR
  • Other imaging suggesting sella (pituitary) mass

INDICATIONS FOR TEMPORAL/MASTOID/INTERNAL AUDITORY CANAL CT

Hearing loss (documented on audiogram)^{31, 32}

• Asymmetric sensorineural when MRI is contraindicated^{33, 34}
• Conductive or mixed³⁵
• Congenita^l35
• Cochlear implant evaluation³⁶

Tinnitus^37-39

• Pulsatile tinnitus with concern for osseous pathology of the temporal bone
• Unilateral non-pulsatile tinnitus and MRI is contraindicated or cannot be performed

Ear Infection

• Clinical suspicion of acute mastoiditis as a complication of acute otitis media^40-43
  • Systemic illness or toxic appearance 
  • Signs of extracranial complications (e.g., postauricular swelling/erythema, auricular protrusion, retro-orbital pain, hearing loss, tinnitus, vertigo, nystagmus)
  • Not responding to treatment

Note: MRI is also indicated if there are signs of intracranial complications (e.g., meningeal signs, cranial nerve deficits, focal neurological findings, altered mental status). This is most common in the pediatric population

• Chronic Otitis Media (with or without cholesteatoma on exam)^{42, 44}
  • Failed treatment for acute otitis media

Cholesteatoma^{45, 46}

CSF Otorrhea^{47, 48}

• When looking to characterize a bony defect (for intermittent leaks and complex cases consider CT/MR/Nuclear Cisternography). CSF fluid should always be confirmed with laboratory testing (Beta-2 transferrin assay.)

Temporal Bone Fracture^49-51

• Suspected based on mechanism of injury OR
• Indeterminate findings on initial imaging OR
• For further evaluation of a known fracture for treatment or surgical planning

Vascular Indications^{52, 53}

• Suspected or known with need for further evaluation
  • Dehiscence of the jugular bulb or carotid canal OR
  • Other vascular anomalies of the temporal bone (i.e., aberrant internal carotid artery, high jugular bulb, persistent stapedial artery, aberrant petrosal sinus)

Peripheral vertigo^{32, 54, 55}

• Based on clinical exam (Head-Impulse with saccade, Spontaneous unidirectional horizontal nystagmus, Dix-Hallpike maneuver); AND
  • Persistent symptoms after a trial of medication and four weeks of vestibular therapy (e.g., Epley’s maneuvers)

Bell’s Palsy/hemifacial spasm if MRI is contraindicated or cannot be performed (for evaluation of the extracranial nerve course)

• If atypical signs, slow resolution beyond three weeks, no improvement at four months, or facial twitching/spasms prior to onset⁵⁶

OTHER INDICATIONS FOR TEMPORAL BONE, MASTOID, ORBIT, SELLA, INTERNAL AUDITORY CANAL CT

Pre-operative/procedural evaluation

• Pre-operative evaluation for a planned surgery or procedure

Post- operative/procedural evaluation

• When imaging, physical, or laboratory findings indicate surgical or procedural complications
• A follow-up study may be needed to help evaluate a patient’s progress after treatment, procedure, intervention, or surgery. Documentation requires a medical reason that clearly indicates why additional imaging is needed for the type and area(s) requested.
   

All other uses of this technology are investigational and/or unproven and therefore considered NOT MEDICALLY NECESSARY. 

References  

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Coding Section 

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 non-affiliated technology evaluation centers, reference to federal regulations, other plan medical policies, and accredited national guidelines.

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