ICD-10-CM > G00-G99 > G40-G47 > G44 > G44.0 > G44.00 G44.00 Cluster headache syndrome, unspecified Non-Billable/Non-Specific Applicable To Ciliary neuralgiaCluster headache NOSHistamine cephalgiaLower half migraineMigrainous neuralgia Codes G44.001Cluster headache syndrome, unspecified, intractableG44.009Cluster headache syndrome, unspecified, not intractable