Table 1 Included studies

Randomised controlled trials:

Karlberg et al. 1996 [26]; Malmström et al. 2007 [44]

n = 34 (88% females)

Mean age: 37

Age range: 25-55

Country: Sweden

Setting: primary care centers and a tertiary referral center

Mobilisation;

Soft tissue therapy (relaxation techniques, stabilisation techniques);

Home training program;

Ergonomic changes at work

Nil

Dizziness frequency; Dizziness intensity; Posturography

- Significantly improved dizziness intensity and neck pain post-treatment (p < 0.05).

- Significantly improved postural sway post-treatment (p < 0.2).

- 14 patients (82%) reported improvements at 6 months post-treatment.^†

- 11 patients (65%) reported improvements in dizziness at 2 year post-treatment.^†

Moderate

Reid et al. 2008 [47]

n = 34 (62% females), 1 drop-out

Mean age: 63.5

Age range: not reported

Country: Australia

Setting: University of Newcastle

Mobilisation (SNAGs)

Nil

DHI;

Dizziness severity (VAS);

Dizziness frequency; Neck pain (VAS); Posturography

- Significantly reduced DHI, dizziness severity, dizziness frequency and neck pain in the treatment group at 6 and 12 weeks post-treatment (p < 0.05).

- No difference in dizziness severity at 12 weeks post-treatment.

- No difference in dizziness frequency at either 6 or 12 weeks post-treatment.

Good

Kang, Wang and Ye 2008 [48]

n = 76 (49% females)

Mean age: 32.4

Age range: 18-45

Country: China

Setting: hospital

Group A:

Spinal manipulation

Group B:

Acupressure

Nil

TCD-US;

TCM syndrome diagnostic criteria

- Significantly reduced VBA blood flow velocity post-treatment in both groups (p < 0.01).

- Significantly larger reduction in left and right vertebral artery blood flow velocity in Group B compared with Group A (p < 0.01).

- Group differences remained statistically significant at a 6-month follow-up.

Moderate

Fang 2010 [49]

n = 168 (73% females)

Mean age: 37.5

Age range: not reported

Country: China

Setting: hospital

Treatment group:

Spinal manipulation;

Soft tissue therapy

Control group:

TCM medication

Nil

CVSFAS;

Colour Doppler ultrasonography

- Significant improvements in dizziness (p < 0.01), shoulder/neck pain (p < 0.05), and headache (p < 0.01) post-treatment.

- Significant reduction of cervical artery spasm index and atlantoaxial displacement index in the treatment group post-treatment (p < 0.05).

Moderate

Du et al. 2010 [50]

n = 70 (54% females)

Mean age: 37.6

Age range: 21-45

Country: China

Setting: hospital

Treatment group:

Spinal manipulation;

Soft tissue therapy

Control group:

Traction;

Medication

Nil

CVSFAS;

Radiography;

TCD-US;

TCM syndrome diagnostic criteria

- Significant improvements in dizziness scores, vertebral displacement post-treatment (p < 0.01).

- Significantly reduced left and right vertebral artery blood flow velocity post-treatment (p < 0.01).

- Significantly improved clinical outcomes six months post-treatment (p < 0.01).

Moderate

Prospective cohort studies:

Konrad and Gerencser 1990 [51]

n = 54 (74% females)

Mean age: 34.7

Age range: not reported

Country: Hungary

Setting: hospital

Mobilisation;

Manipulation

Nil

Dizziness (instrument not specifically stated);

Electronystagmography

- 40 patients (74%) experienced improvement of dizziness post-treatment.^†

Poor

Mahlstedt, Westhofen and König 1992 [52]

n = 28 (gender distribution not reported)

Mean age: not reported

Age range not reported

Country: Germany

Setting: not reported

Spinal manipulation

Nil

No information provided

- 19 patients (68%) reported reduced dizziness post-treatment.^†

Poor

Uhlemann et al. 1993 [53]

n = 12* (gender distribution not reported)

Mean age: 40.7

Age range: not reported

Country: Germany

Setting: not reported

Mobilisation;

Spinal manipulation (traction)

Nil

Cervical turn test

- 5 out of 9 patients went from testing positive to testing negative on the cervical turn test post-treatment.

Poor

Bracher et al. 2000 [54]

n = 15 (80% females), 3 drop-outs

Mean age: 41

Age range: 27-82

Country: Brazil

Setting: chiropractic clinic

Spinal manipulation;

Soft tissue therapy; Electrotherapy;

Labyrinth sedation medication;

sEMG biofeedback;

Exercise program

Nil

Dizziness (instrument not specifically stated; "improvement of symptoms was based on patient's reports")

- 9 patients (60%) reported complete remission of dizziness, 3 patients (20%) reported consistent improvement with rare recurrence of episodes of mild intensity, and 3 patients (20%) reported no change.^†

Poor

Hülse and Hölzl 2000 [55]

n = 67 (52% females)

Mean age: 49

Age range: 18-66

Country: Germany

Setting: not reported

Soft tissue therapy (traction massage, PIR,

occipital-base-release technique, atlas-impulse-therapy)

Nil

Craniocorpography; Posturography

- Significant improvements in pathological vestibulospinal reactions found post-treatment (p < 0.001).

Poor

Chen and Zhan 2003 [56]

n = 16 (38% females)

Mean age: 42.4

Age range: 38-58

Country: China

Setting: hospital

Spinal manipulation;

Soft tissue therapy

Nil

TCD-US;

Radiography;

TCM syndrome diagnostic criteria

- 14 patients (87.5%) reported marked improvement or complete remission of symptoms.

- Significantly decreased vertebral artery mean blood flow velocity post-treatment (p < 0.05).

- Significantly reduced vertebral displacement post-treatment (p < 0.05).

Poor

Wu et al. 2006 [45];

Wu et al. 2008 [46]

n = 121 (73% females)

Mean age: not reported

Age range: 20-71

Country: China

Setting: hospital

Tuina manipulation therapy (pressing-kneading manipulation applied continuously to bilateral vertebrae for 5 minutes)

Nil

Custom-made instrument to measure skull 3D motion and head repositioning.

- Significant improvements in skull spatial offset repositioning ability post-manipulation (p < 0.01).

Poor

Strunk and Hawk 2009 [57]

n = 21 (63% females), 2 drop-outs

Mean age: 70

Age range: 44-85

Country: USA (California)

Setting: Cleveland Chiropractic College

Spinal manipulation;

Soft tissue therapy (myofascial release, PIR, and heat or cold therapy)

Nil

DHI

SF-BBS

NDI

- Improved DHI and SF-BBS scores.^†

- Improved balance.^†

- Decreased dizziness and neck pain.^†

Moderate