Cervicocranial syndrome (or craniocervical junction syndrome, CCJ) is headache caused by a cervical spine condition. The pain is typically asymmetric, sometimes one-sided, and can be provoked by certain neck motions, poor head posture, or pressure on trigger points in the neck. Diagnosis is made by joint reference to the criteria of the International Headache Society and the Cervicogenic Headache International Study Group. Differential diagnosis should exclude secondary organic causes, particularly expansionary processes in the posterior cranial fossa and subarachnoidal haemorrhage. Neurological examination results of CCJ patients should be normal, but a specialized manual myoskeletal examination often finds abnormality in the cervical spine. Computed tomography (CT) or magnetic resonance (MR) imaging is important to distinguish from other causes of pain, for which different treatments are indicated. Successful treatment of CCJ usually requires a complex multi-factor approach combining pharmaceutical treatment with rehabilitation and / or manual therapy.
Source: http://www.medicinapropraxi.cz/pdfs/med/2011/04/07.pdf (in Czech)
Further Reading: Cervicocranial Syndrome on the English Wikipedia