The Line Bisection Test is a test is a quick measure to detect the presence of unilateral spatial neglect (USN). To complete the test, one must place a mark with a pencil through the center of a series of horizontal lines. Usually, a displacement of the bisection mark towards the side of the brain lesion is interpreted as a symptom of neglect.
There are many versions of the Line Bisection Test, and the procedures are rarely standardized, with the exception of when the Line Bisection Test is used as an item within a standardized test battery (Plummer, Morris, & Dunai, 2003).
The relationship between abnormal line bisection and visual neglect has been observed for over a century (e.g. Axenfeld, 1894; Liepmann & Kalmus, 1900). In 1980, Schenkenberg, Bradford, and Ajax formally evaluated this method of detecting the presence of visual neglect in patients with lesions of the non-dominant hemisphere, and are thought to be the first to statistically evaluate this method.
Patients are asked to place a mark with a pencil (with their preferred or unaffected hand) through the center of a series of 18 horizontal lines on an 11x 8.5-inch page.
The test is scored by measuring the deviation of the bisection from the true center of the line. A deviation of more than 6 mm from the midpoint indicates USN. Omission of two or more lines on one half of the page indicates USN.
The test takes less than 5 minutes to complete.
None typically reported.
11x 8.5-inch page of paper with 18 horizontal lines
The Line Bisection Test can be presented in various forms. Some studies use 18 horizontal lines, while others have used a single line (Parton, Malhotra & Husain, 2004), or a series of 10 lines (Ferber & Karnath, 2001). The Line Bisection Test is also offered as part of some standardized test batteries such as within the Behavioural Inattention Test (Wilson, Cockburn, Halligan, 1987; Schubert & Spatt, 2001).
Can be used with: Patients with stroke.
Patients must be able to hold a pencil in order to complete the task (the presence of apraxia may impair this ability).
Should not be used with:
The Line Bisection Test should be used with caution in the clinical diagnosis of spatial neglect:
Ferber and Karnath (2001) found that deviation in line bisection was not apparent in 40% of the patients in their sample that had severe neglect. In comparison, each of the four cancellation tests administered in this study (Line Crossing, Letter Cancellation, Star Cancellation and Bells Test) missed 6% of the subjects and may be preferred over the Line Bisection Test for diagnosing USN.
Performance on the Line Bisection Test may be influenced by or may be indicative of other syndromes besides spatial neglect, such as hemianopia (damage of optic pathways that result in loss of vision in half of the visual field) (Ferber & Karnath, 2001). Consequently, the Line Bisection Test is not a highly specific measure of USN.