Inclusion criteria:

Unilateral CGH presentation,

Age group above 18 years’ old,

History of chronic CGH (> 3 months),

CGH intensity ≥ 3 on a 10-point scale,

CGH owing to cervical spine (neck) dysfunction,

Reduced cervical motion in FRT and neck pain followed by headache,

Neck stiffness and movement restriction patients were allowed to participate in the study, and

No fracture, osteoporosis, deformities, and abnormalities on cervical spine image.

Exclusion criteria:

Participants with other types of headache (migraine),

Headache owing to other causes (sinus, tumor, neural, and tempero-mandibular joint issues),

Had any type of physical therapy treatment in the past 3 months,

Any contraindications to manual and manipulative therapy (fracture, instability, osteoporosis, arthropathy, and neural symptoms),

Taking analgesics or corticosteroids and migraine-specific medications, such as triptans,

Metastasis,

Cardiac conditions (stroke, hypertension, and syncope),

Neurological conditions (radiculopathy, myelopathy, and disc prolapse),

Spinal cord problems, and

Previous brain and spinal cord surgery patients were excluded.

The flow of the study program was recorded in accordance with the Consolidated Standards of Reporting Trials (CONSORT) guidelines and is shown in Fig. 1. Eligible participants were recruited from the University Hospital and King Khalid Hospital, Al-Kharj, Saudi Arabia.

Fig. 1

Flow chart showing the study details

Interventions

In addition to the regular interventions, participants in the SMT group received spinal manipulation therapy, while participants in the SMT + ISM group received both SMT and ISM as part of their intervention. The two treatment groups received similar treatments, except for the addition of ISM, with respect to time allocated and information provided.

As per the study protocol, the interventions were provided by licensed physical therapists with 15–20 years of clinical experience in manual and manipulation therapy techniques. All participants in both groups were compensated by receiving free physical therapy treatment. First, the cervical vertebra joints and neck muscles of each participant were examined to identify joint dysfunction. Next, patients underwent 10 min of hydrocollator hot pack treatment at the base of the neck and upper shoulders to relax the muscles. After the hot pack application, the respective mobilization approaches were provided according to the study protocol. Participants were also taught and instructed to perform neck isometric exercises three times a day, every day. Intervention bias was minimized by using fixed treatment procedures, and standard forms were used to document treatment details and follow-up. All participants were instructed not to seek other forms of treatment during the study period. The treatment was administered four times per week for 4 weeks in both groups.

Spinal Manipulation Therapy

The SMT provided in the study followed the description by Peterson and Bergman. A trained manipulative therapist performed the technique after assessing each participant at every visit through physical examination and proper palpation. The therapist identified dysfunction sites in the cervical region using the FRT test and manipulated the region according to the study recommendations. Manipulation was not provided if the participant presented with any new contraindications to SMT or lacked clinical indications for SMT.

The participant lay comfortably in a supine position with arms and legs at the side and neck in a neutral position. The therapist stood at the head of the patient and cradled the patient’s head, placing one hand over the chin and the other on the posterior aspect of the occiput. Manipulation was performed in both directions, primarily targeting the upper cervical (C1–C2) vertebra. The movement was first directed away from the pain and then toward the pain. This bimanual technique involved premanipulation rotation of 30–45°, with the manipulation performed toward the side of pain using high-velocity, low-amplitude thrusts. The range of rotation depended on the level of the target vertebrae [20]. The intervention followed the World Health Organization (WHO) guidelines on basic training and safety in spinal manipulation to prevent undue effects.

Instrument-Assisted Soft-Tissue Mobilization

In ISM, the participant sat in a relaxed position, resting the forehead on folded hands placed on a plinth. Skin softener (Himalaya massage cream—Gold, New Delhi, India) was applied over the suboccipital and lateral neck regions to reduce friction and discomfort during the procedure. The M2T blade (Ontario, Canada), sterilized with alcohol-soaked cotton, was used for the procedure. The soft tissue restrictions in the cervical region were identified, and the restricted sites were noted. A fascial release was then performed using the M2T blade at a 45° angle in different planes, with strokes applied in the direction of the neck muscles without eliciting any symptoms. The technique targeted the levator scapula, sternocleidomastoid, scalene, and upper trapezius muscles from origin to insertion on both sides for 8 min. The same technique was applied over the longissimus capitis, splenius capitis, semispinalis capitis, and suboccipital muscles in a centripetal direction, repeated three times. The procedure was stopped immediately if the participant experienced any adverse effects, such as increased pain, discomfort, or abnormal sensations [21]. Participants were informed that mild soreness after manual therapy is normal.

All participants in both groups also received heat therapy. They were placed in a supine position with the neck in a neutral position. A heated hydrocollator pack, wrapped in a towel to protect the skin, was gently placed on the cervical region (base of the neck and upper shoulders), where muscle tension was likely contributing to the headache. The temperature was adjusted for comfort, and the pack was left in place for 10 min. Participants were also instructed to perform neck isometric exercises three times daily. They were to place the palm over the forehead and resist forward neck movement, holding the resistance for 10 s and repeating it 15 times. Similar resistance exercises were performed on the back and both sides of the head. Participants were advised to continue these exercises even after completing the 4 weeks of treatment. The intervention schedule is depicted in Fig. 2.

Fig. 2

The study intervention schedule

Outcomes

The outcomes were measured at baseline, after 4 weeks, and at 6 months. These intervals provided a balanced view of both the immediate and longer-lasting effects of the interventions, which was crucial for understanding the efficacy and safety of these interventions in cervicogenic headache.

Primary Outcome

CGH frequency This was a self-reported measure, where patients with cervicogenic headache were asked to report the number of CGH days over 4 weeks in a medical logbook [22].

Secondary Outcome

CGH pain The intensity of CGH pain was measured using a 10-point visual analogue scale (VAS). Patients were asked to indicate their pain intensity on a 10 point scale, where 0 denoted “no pain” and 10 denoted “maximum intolerable pain.” This was a valid and reliable tool for measuring CGH pain intensity [23].

CGH disability The six-item headache impact test (HIT) questionnaire was used to measure the disability status of patients with cervicogenic headache. It was a valid and reliable tool [24].

Neck pain frequency This was a self-reported measure, where patients were asked to report the number of neck pain days over 4 weeks in a medical logbook [22].

Neck pain intensity The intensity of neck pain was measured using a 10-point visual analogue scale (VAS). Patients were asked to indicate their pain intensity on a 10 point scale, where 0 denoted “no pain” and 10 denoted “maximum intolerable pain.” This was a valid and reliable tool for measuring neck pain intensity [23].

Neck pain threshold The pain threshold was measured with a Digital Algometer (Wagner, Model FPX, USA), applied over a standard location (a trigger point on the upper trapezius muscle) in the neck region identified through palpation. This was a reliable and valid tool for measuring pain threshold [25].

Neck disability index (NDI) This was a valid and reliable self-reporting questionnaire consisting of 10 items, measured on a 0–5-point scale. Disability grades were determined on the basis of scores as follows: 0–4: no disability, 5–14: mild disability, 15–24: moderate disability, 25–34: severe disability, and 34 or more: complete disability [26].

Quality of life The EuroQol 5D (covering mobility, self-care, usual activities, pain/discomfort, and anxiety/depression) was used as a psychometric questionnaire to measure the overall quality of life in patients with cervicogenic headache. The scale ranged from 0, representing the worst imaginable health state, to 100, representing the best imaginable health state [27].

Sample Size

The sample size was calculated using data from a previous study on the primary outcome of CGH days [28]. The required sample size was determined by assuming 80% power using a two-tailed test with a significance level of 0.05. To detect a minimum effect size of 1.5 CGH days, with a mean difference of 3.5 CGH days and a standard deviation of 0.7, the required sample size was 29 participants in each group. After considering a 10% dropout rate, the required sample size in each group increased to 32.

Randomization

An individual not involved in data collection performed the randomization. A total of 64 participants were randomized into SMT and SMT + ISM groups with a 1:1 allocation ratio. Randomization was conducted using a computer-generated random table, and participants were assigned to one of the two groups through sealed envelopes. All prospective participants who met the eligibility criteria were included in the study.

Blinding

Owing to the nature of the study, it was not feasible to blind the treating therapists or the participants. However, the therapists who assessed the outcome variables at baseline, 4 weeks, and 6 months were blinded. The therapist providing treatment and the one measuring outcomes were different individuals. The outcome-measuring therapist remained blinded to the participants’ group allocation throughout the study. Participants were also asked not to discuss their treatment with peers or the outcome-measuring therapist. Additionally, the authors did not have access to information that could identify individual participants during or after data collection.

Statistical Methods

Demographic characteristics of the participants were analyzed to determine the homogeneity of the study using the Kolmogorov–Smirnov test. Outcome data were presented as mean and standard deviation with a 95% confidence interval. The treatment effects at various intervals were analyzed using a 2 × 3 mixed model analysis of variance (ANOVA), with the treatment group (spinal manipulation and spinal manipulation with ISM) and time intervals (baseline, 4 weeks, and 6 months). Repeated measures ANOVA was performed to identify significant differences within the groups. An independent t-test was used for between-group comparisons, with statistical significance set at p < 0.05. All statistical analyses were conducted using SPSS software (version 20.0), SPSS Inc., Chicago, Illinois, USA.