I. Introduction

Apraxia, which literally means “no work”, involves the disturbance of purposeful expressive functions^[1] . Neither constructional apraxia nor dressing apraxia is a strict form of apraxia with regards to a loss of previous learned behavior^[2] . That is, patients with normal motor function cannot be programmed to perform such purposeful expressions, e.g., finger figuring^[3], cubic block sign test, and drawing a cube^[4] . Testing of such parameters, i.e., copying a projected cube, is simple and effective for diagnosing constructional apraxia^[5-9], particularly in out patients. However, evaluation of these tests is achieved qualitatively and subjectively using a scoring method^[8,9], increasing its objective bias and limiting diagnosis to exasperated cases. To the best of our knowledge, no subjective quantitative analysis has been reported for the cube copying test. Therefore, the aim of this study was to develop a quantitative method to examine mild cognitive impairment.

II. Materials and Methods

Study Design

Each subject was presented a projected cube （with one side 4 cm long） on a sheet of paper and asked to draw （“copy”） it within a certain area on the same sheet, as shown in ^{(Fig. 1A)}. The sheet was placed on a digitizer while the subject drew the cube. The figure drawn by the subject was digitized and stored in the memory of the digitizer for further study.

Subjects

The study enrolled 19 out patients, aged 68 to 92 years, who visited our hospital with a chief complaint of memory disturbance or fear of dementia. For a control group, the study also enrolled 9 younger patients, aged from 21 to 60 years, who visited the hospital with minor head trauma or dizziness, but no neurological deficit. Each subject was informed the purpose of the study and provided written informed consent before performing the test.

Analysis

The digital data were imported to a personal computer with minimal patient identification, i.e., age, gender, and score of Hasegawa’s Dementia Scale-revised （HDS-R） for elderly subjects. The size of the drawn figure was adjusted to that of the example figure and the lines of the drawn figure were smoothed. The following six correlation coefficients （CCs） were calculated for each drawn figure using MatLabＲ （R2007b, Math Works, USA）: CC1, between the drawn and example figures ^{(Fig. 1B)}; CC-2, between the drawn figure and its 180° rotation ^{(Fig. 1C)}; CC-3, between the right and left halves of the drawn figure ^{(Fig. 2A)}; CC-4, between the upper and lower halves of the drawn figure ^{(Fig. 2B)}; CC-5, between the right upper quadrant and left lower quadrant, which was rotated 180°, of the drawn figure ^{(Fig. 2C)}; and CC-6, between the right lower quadrant and left upper quadrant, which was rotated 180°, of the drawn figure ^{(Fig. 2D)}. The analysis of variance was done for the CCs, and significant differences were determined using the Piason’s test.

III. Results

Figures 1B ^{(Fig. 1B)}, 1C ^{(Fig. 1C)}, and 2 ^{(Fig. 2)} show the process to obtain the 6 CCs for subject 6 in Table 1 ^{(Table 1)} whose HDS-R 23/30 and CT findings showed mild cortical atrophy. In this example, CC-1, between the drawn and sample figure, was 0.36 and CC-2, between the drawn figure and its 180° rotation,was 0.43; the significance level was 0.009 for the Piason’s test （n＝215×223, t＝1.96）. CC-3, between the left and 180°-rotatedright halves of the drawn figure, was 0.46; the significant level was 0.013 （n＝108×112, t＝1.96）. CC-4, between the upper and 180°-rotated lower halves of the drawn figure, was 0.49; the significant level was 0.018 （n＝107×111, t＝1.96）. CC-5, between the left upper and the 180°-rotated right lower quadrants of the drawn figure, was 0.38. CC-6, between the left lower and the 180°-rotated right upper quadrants of the drawn figure was 0.49. Both had a significant level of 0.018 （n＝107×112, t＝1.96）. Figure 3 ^{(Fig. 3)} shows examples of cubes drawn by the elderly group. Most of the drawn cubes were moderately deteriorated （a-h）, while two （i and j）, drawn by 91- and 92-year-old subjects, respectively, were relative to controls. Tables 1 ^{(Table 1)} and 2 ^{(Table 2)} show the CCs for the elderly and younger groups, respectively. Significant differences were observed between these groups （P＜0.0001）. There were no significant correlations between age and CC, and between HDS-R scores and CC.

IV. Discussion

Quantitative analysis found significant differences between the elderly and younger control groups. Based on this analysis, no subjects were diagnosed with typical constructional apraxia; however, as seen in Fig. 3 ^{(Fig. 3)} , drawing ability was deteriorated for some elderly subjects who showed mild deterioration for HDS-R and diffuse abnormality in the CT scan. HDS-R is a simple and adequate method to screen for dementia. Currently, this scale is frequently used by family doctors. However, HDS-R was developed to screen for dementia without a performance test^[10]. Our results showed no relationship between HDS-R and CC, indicating the addition of a performance test would be beneficial for elderly patients. Similar to the mini-mental state examination, another simple screening test using a drawing test^[11], HDS-R, especially for elderly patients, should be used together with a drawing test. Posterior parietal cortex plays a major role in drawing by copying^[12]. Typical constructional apraxia in patients has been associated with parietal lesions^[5,6]. In this study, no solitary lesions over the parietal areas were noted for elderly subjects on CT, and no elderly subjects showed spatial neglect. As functional magnetic resonance imaging, single photon emission computed tomography, or positron emission tomography could not be performed in our hospital, apraxia could not be confirmed. However, mild cognitive impairment is speculated from the CT findings and moderate deterioration in HDS-R. This study proposes inclusion of a cube copying test with HDS-R for elderly patients. We are currently investigating the implementation of this cube copying test for sensitive screening of mild cognitive impairment.

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