cervicogenic patients will undergo SNAGs treatment. Based on personal history, the offending active cervical movement (i.e. the movement predominantly causing dizziness) will be identified and treatment direction will be determined. As suggested, the active movement to most likely cause dizziness is cervical extension, though also rotation or flexion will be shown to provoke it. With the participant in an upright sitting position, a skilled physiotherapist (blinded to the allocation) will apply a sustained passive accessory movement (glide) while the participant will be asked to move actively as allowed by his/her physiological range in the direction producing their symptoms. This procedure will be repeated six times.

cervicogenic patients will receive a sham treatment, carried out by the another skilled therapist (blinded to the allocation) and consisting in exposition to a detuned laser. A laser - deactivated by the manufacturer in order to produce no effective emission - will appear to operate normally, emitting a light signal and a beeping sound. Such procedure - which was shown to not activate somatosensory receptors and to have a very strong placebo effect - will be used for six applications, lasting 20 seconds, on various sites on the upper cervical spine, at a distance of 0.5-1cm from the skin.

a sustained passive accessory movement (glide), i.e. SNAGs, will be applied by the physiotherapist while the participant will be asked to move actively as allowed by his/her physiological range in the direction producing his symptoms.

Study of the surface of the ellipse of confidence (calculated in mm) by means of static posturography platform will be used to assess the sway of the posture. Low levels of outcomes indicate better performances. No specific reference ranges are given in literature.

A cervical range of motion (CROM) goniometer, which has been shown to be a reliable tool with good validity, will be used to measure (in degrees) cervical spine movements. Active flexion, extension, left and right rotation, and left and right lateral flexion will be measured three times and then averaged. Low levels of outcomes indicate worse performances. No specific reference ranges are given in literature.

The Italian Dizziness Handicap Inventory (DHI) wil be used to assess the self-report dizziness handicap. It consists of 25 questions designed to assess a patient's functional (nine questions), emotional (nine questions), and physical (seven questions) limitations; absolute scores range from 0 to 100, with moderate and severe disability usually associated with scores above 30 and 60, respectively