Is medical necessity met for intraoperative neurophysiological monitoring for a patient with a benign neoplasm of cranial nerves (D33.3) undergoing a retrosigmoid craniotomy for excision of vestibular schwannoma?

Medical Necessity for Intraoperative Neurophysiological Monitoring in Vestibular Schwannoma Surgery

Medical necessity is MET for codes 95941,95940,95867, and 95938 for this patient undergoing retrosigmoid craniotomy for excision of a large vestibular schwannoma with brainstem compression. However, code 95937 (neuromuscular junction testing) does NOT meet medical necessity criteria for this indication.

Rationale for Approval

Facial Nerve EMG Monitoring (95867) - APPROVED

The European Association of Neuro-Oncology (EANO) 2020 guidelines explicitly state that intraoperative neurophysiological monitoring is mandatory for vestibular schwannoma surgery and should include facial nerve monitoring comprising direct electrical stimulation and free-running electromyography 1. This is classified as evidence class III, recommendation level B 1.

• The Congress of Neurological Surgeons (CNS) 2018 guidelines provide Level 3 evidence that intraoperative cranial nerve monitoring of the facial nerve during VS surgery leads to better facial function outcomes 1.
• For large lesions specifically, the EANO guidelines recommend electromyography of the lower cranial nerves (evidence class IV, good practice point) 1.
• This patient has a large vestibular schwannoma with brainstem compression, making facial nerve monitoring particularly critical for preserving function and preventing permanent facial paralysis 1.

Somatosensory Evoked Potentials (95938) - APPROVED

SSEP monitoring is medically necessary for intracranial procedures when the integrity of neural structures is at risk, which clearly applies to this posterior fossa surgery with brainstem compression 1.

• The EANO 2020 guidelines state that intraoperative monitoring for VS surgery should include somatosensory evoked potentials (evidence class III, recommendation level B) 1.
• The Aetna policy correctly references that SSEPs are considered medically necessary for intraoperative monitoring under certain conditions during intracranial surgery in the posterior fossa 1.
• Given this patient's large tumor with brainstem compression and multiple neurological symptoms (trigeminal neuralgia, facial numbness, dysphagia, gait instability), SSEP monitoring is appropriate to detect adverse changes in spinal cord and brainstem function before they become irreversible 1.

Continuous Monitoring Codes (95940 and 95941) - APPROVED

Both continuous monitoring codes are appropriate for this complex posterior fossa surgery requiring extended monitoring time 1.

• Code 95940 (one-on-one monitoring in the operating room per 15 minutes) and 95941 (remote/nearby monitoring per hour) are standard billing practices for the extended duration required in vestibular schwannoma resection 1.
• The EANO guidelines emphasize that intraoperative neurophysiological monitoring is mandatory for VS surgery, implicitly supporting the need for continuous monitoring throughout the procedure 1.

Rationale for Denial

Neuromuscular Junction Testing (95937) - DENIED

The Aetna Clinical Policy Bulletin 0697 explicitly states there is insufficient evidence for neuromuscular junction testing (train of four monitoring) and considers it integral to anesthesia administration, not separately reimbursable [@case summary provided].

• Neuromuscular junction testing monitors the degree of neuromuscular blockade from anesthetic agents, not neural pathway integrity [@case summary].
• This monitoring is considered a standard component of anesthesia care and does not provide specific information about cranial nerve or neural structure preservation during tumor resection [@case summary].
• The policy specifically lists CPT code 95937 as NOT covered for intraoperative neurophysiological monitoring [@case summary].

Clinical Context Supporting Medical Necessity

This 47-year-old female presents with:

• Large vestibular schwannoma with brainstem compression - a clear indication for comprehensive intraoperative monitoring 1
• Multiple cranial nerve symptoms including trigeminal neuralgia, facial numbness, dysphagia, and hearing loss [@case summary]
• Gait instability and disequilibrium indicating brainstem involvement [@case summary]

The tumor size and brainstem compression place this patient at high risk for neurological injury during surgical resection, making comprehensive monitoring not just appropriate but mandatory according to current guidelines 1.

Important Caveats

• The technical (TC) and professional (26) component modifiers for codes 95938,95867, and 95937 should be reviewed to ensure appropriate billing based on who performed the technical monitoring versus interpretation [@case summary].
• While hearing preservation monitoring (brainstem auditory evoked responses) is also recommended by EANO guidelines when hearing preservation is attempted, this was not specifically queried in the authorization request 1.
• The diagnosis code D33.3 (benign neoplasm of cranial nerves) is appropriate for vestibular schwannoma, though some policies may require more specific documentation of the vestibular nerve origin [@case summary].

Final Determination: Approve codes 95941,95940,95867 (x2), and 95938 (x2) with both TC and 26 modifiers. Deny code 95937 (x2) with both TC and 26 modifiers as not medically necessary per policy criteria 1.