Does G0251 require prior authorization?

No, G0251 does not require prior authorization (high confidence). Covered without prior authorization.

`G0251`, Linear accelerator based stereotactic radiosurgery, delivery including

HCPCS/CPT

No Prior Auth Required

Covered without prior authorization (high confidence)

Trigeminal/occipital radiofrequency or nerve ablation/neurectomy: documentation of diagnostic nerve blocks demonstrating temporary relief, prior conservative treatments attempted and failed, technique details, and baseline/ongoing outcome measures.
No documentation requirements are stated in this excerpt (bibliography only).
nVNS (gammaCore): diagnosis of episodic cluster headache for acute indication (adult patients), record of device prescription and patient training, documentation of attacks treated and response rates, and for prophylactic/adjunctive use in cCH documentation of prior treatments and rationale for adjunctive therapy (PREVA-like paradigms).
VTA-DBS (and other invasive neuromodulation like ONS/DBS): documentation of medically refractory chronic cluster headache with failure of multiple adequate trials of standard therapies, prior trial/failure of occipital nerve stimulation (if applicable), multidisciplinary team evaluation (headache neurologist and functional neurosurgeon), baseline headache frequency/severity, and detailed informed consent describing investigational status and risks.

Temporal artery biopsy — CPT 37609: "Ligation or biopsy, temporal artery [covered for biopsy to rule out temporal arteritis]" (ICD-10: M31.6 Other giant cell arteritis [suspected temporal arteritis] listed as an ICD-10 code covered if selection criteria are met).
Botulinum toxin: "Botulinum toxin (however, botulinum toxin is considered medically necessary for chronic migraine headache when criteria in CPB 0113 - Botulinum Toxin are met)" (i.e., botulinum toxin is covered for chronic migraine only when CPB 0113 criteria are satisfied).
Occipital nerve block (greater occipital nerve) — CPT 64405: "Injection, anesthetic agent; greater occipital nerve" — listed as "CPT codes covered if selection criteria are met" for occipital neuralgia.
"Occipital nerve block is allowable only for diagnosing occipital neuralgia" (explicit policy statement).
ICD-10 codes explicitly listed as covered if selection criteria are met: "M31.6 Other giant cell arteritis [suspected temporal arteritis]" (general section) and "M54.81 Occipital neuralgia" (occipital neuralgia section).
Occipital nerve stimulation (ONS) is a therapeutic option for patients with medically refractory occipital neuralgia (Sweet et al, 2015: "the use of ONS is a therapeutic option for patients with medically refractory ON").

AETNA-CPB-0707, Headaches: Invasive Procedures

AETNA-CPB-0374, Trigeminal Neuralgia: Treatments

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