Guidelines and quality measures for the diagnosis of optic ataxia

Abstract

Since the first description of a systematic mis-reaching by Bálint in 1909, a reasonable number of patients showing a similar phenomenology, later termed optic ataxia (OA), has been described. However, there is surprising inconsistency regarding the behavioral measures that are used to detect OA in experimental and clinical reports, if the respective measures are reported at all. A typical screening method that was presumably used by most researchers and clinicians, reaching for a target object in the peripheral visual space, has never been evaluated. We developed a set of instructions and evaluation criteria for the scoring of a semi-standardized version of this reaching task. We tested 36 healthy participants, a group of 52 acute and chronic stroke patients, and 24 patients suffering from cerebellar ataxia. We found a high interrater reliability and a moderate test-retest reliability comparable to other clinical instruments in the stroke sample. The calculation of cut-off thresholds based on healthy control and cerebellar patient data showed an unexpected high number of false positives in these samples due to individual outliers that made a considerable number of errors in peripheral reaching. This study provides first empirical data from large control and patient groups for a screening procedure that seems to be widely used but rarely explicitly reported and prepares the grounds for its use as a standard tool for the description of patients who are included in single case or group studies addressing optic ataxia similar to the use of neglect, extinction, or apraxia screening tools.

Pure optic ataxia and visual hemiagnosia – extending the dual visual hypothesis

“…By conducting optic the ataxia assessment suggested by Borchers et al . (), we found OA for the right hemifield in our patient. The patient showed both a hemifield and a hand effect, that is, significant misreaching towards right‐sided objects (field effect) with her right hand (hand effect), and a slight misreaching towards right‐sided objects when reaching with her left hand in the peripheral vision condition.…”

“…The performance of our patient was compared with the one of the control group reported in Borchers et al . (), using the single case method developed by Crawford, Garthwaite, and Wood (). The procedure provides a point estimate of the abnormality of the scores.…”

“…Clinical eye movement examination of saccades and smooth pursuit was normal. About 3 months after the haemorrhage, the patient underwent a comprehensive neuropsychological assessment, including a standardized test of OA (Borchers, Muller, Synofzik, & Himmelbach, 2013) and a series of experiments specifically designed for testing visual hemiagnosia (Pflugshaupt et al, 2016).…”

“…Optic ataxia we assessed as suggested by Borchers et al (2013). In this test, the patient is asked to reach and grasp a wooden pole, as quickly and accurately as possible (length of the pole of 20 cm [7.9″]: 8 cm [3.2″] for the examiner to hold, and 12 cm [4.7″] for the patient to grasp; diameter of 2.8 cm [1.1″]).…”

“…The whole test was videotaped and was subsequently rated offline by two independent judges, to test interrater reliability. A graded rating scheme for movement errors was used, with categories ranging between 0 (no errors) and 3 (gross errors) (for a detailed description, see table 2 in Borchers et al, 2013). In summary, one point was given when the patient grasped the pole at the lower edge only, or faltered/hesitated during the hand movement towards the target.…”