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Letter to the editor
Different impact of prism adaptation
rehabilitation in spatial neglect and
anosognosia for hemiplegia
Dear Editor
Anosognosia for hemiplegia (AHP), the unawareness of one’s
own motor deficits, occurs after brain damage and is frequently
associated with unilateral spatial neglect (USN). Anosognosia is
frequently a transitory manifestation with spontaneous recovery,
which can interfere with rehabilitation [1].
Different behavioural treatments have been proposed to
improve both neglect and anosognosia. To alleviate signs of
USN, one of the most recent effective techniques is prism
adaptation (PA) [2], which is efficacious for most symptoms of
USN. Conversely, PA does not seem to have beneficial effects on
visual perceptual tasks [3] or reflexive orienting of attention [4].
For treating anosognosia, positive outcomes have been reported
using caloric vestibular stimulation [5], transcranial direct current
stimulation (tDCS) [6] and different cognitive procedures [7,8].
To our knowledge, only one study has investigated the efficacy
of PA in USN and anosognosia in the same group of participants.
Both deficits were treated with different rehabilitation techniques
and evaluated before and after each rehabilitation session. The
results showed a different impact of each treatment on anosognosia and USN, which resulted in treatment response bias
[9]. Transient improvement of anosognosia lasting for 48 h was
observed after a PA session.
We lack information on the effect of multiple treatment
sessions with PA on anosognosia. Here, we describe the application
of repetitive PA treatment in a patient with moderate USN and
severe anosognosia.
A 64-year-old man was assessed 90 days after a righthemisphere ischemic stroke encroaching on the inferior frontal
gyrus, putamen and insula. Tract-wise hodological analysis [10]
revealed disconnections of superior longitudinal fasciculus,
inferior fronto-occipital fasciculus and fronto-insular tracts
(Fig. 1). These areas and tracts were previously found associated

with AHP [11] and anosognosia for hemianesthesia (AHA) [12]. On
standard clinical neurological examination, the patient presented
severe hemiplegia, hemianesthesia and hemianopia. During the
same evaluation, he also showed moderate AHP and moderate
AHA. In everyday life, even if limited by hemiplegia, he showed
some severe degree of anosognosia for his motor deficits.
The patient was tested for anosognosia and USN before PA
treatment, 2 days after the end of treatment and 3 weeks later. USN
assessment was performed in each session by tests of letter
cancellation, star cancellation, line bisection, copy drawing and
sentence reading, and the Catherine Bergego functional scale was
administered (Fig. 2a–f). AHP and AHA were assessed by the Visual
Analogue Test for Anosognosia for motor impairment (VATAm)
[13] and the Unawareness of Motor and Somatosensory deficits
after stroke questionnaire (UMAS) [14]. PA treatment was repeated
over 10 sessions, performed twice a day for 5 days by use of 11.38
rightward shift prism goggles. As a sign of correct adaptation, the
after-effect measured with open loop pointing over each session
was significant (P < 0.0001), showing a typical process of
adaptation (Fig. 2g). During the study, the patient received
physical rehabilitation.
The results of repetitive PA treatment showed improvement of
USN (from a global 57% of severity to 15%) with some variability
across tests. The number of omissions decreased significantly in
letter cancellation (x2 = 13.2, P < 0.005) but not star cancellation
(x2 = 3.95, P > 0.05). However, no amelioration of anosognosia was
observed in either of the tests administered (VATAm from 89 to
94%; UMAS 80 to 80%, Fig. 2h), with no substantial difference
between AHP and AHA. The results observed after PA become
substantially stable on follow-up at 3 weeks.
This evaluation, even though limited to one patient, confirms
the efficacy of repeated PA treatment in USN rehabilitation.
Conversely, in this case, we found no amelioration of AHP or AHA.
PA could have a short-term transient effect on anosognosia, as
previously demonstrated [9], but this effect did not last longer and
persisted over repeated treatment. The association between USN
and anosognosia and their specific simultaneous improvement
was found in single case or case series with use of vestibular

Fig. 1. Brain lesion reconstruction in a 64-year-old male with right unilateral spatial neglect (USN) and anosognosia after ischemic stroke. The lesion was identified on CT scan
90 days after the stroke and mapped into standard Montreal Neurological Institute (MNI) space. The lesion was superimposed onto a 2D axial rendering of the MNI
representative brain in stereotactic space by using MRIcron software. The numbered slices correspond to Z-coordinates.
https://doi.org/10.1016/j.rehab.2017.12.007
1877-0657/ C 2018 Elsevier Masson SAS. All rights reserved.

Please cite this article in press as: Facchin A, Beschin N. Different impact of prism adaptation rehabilitation in spatial neglect and
anosognosia for hemiplegia. Ann Phys Rehabil Med (2018), https://doi.org/10.1016/j.rehab.2017.12.007

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REHAB-1153; No. of Pages 2
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Fig. 2. Composite results from testing for the patient; a–f: representation of results from the single neuropsychological test over sessions of evaluation for (a) letter
cancellation; b: star cancellation; c: line bisection; d: Gainotti figure-copy drawing and (e) sentence reading; f: Catherine Bergego functional scale (patient report); g: aftereffect of prism adaptation (open-loop pointing) for each prism adaptation (PA) session; h: representation of evolution over sessions testing unilateral spatial neglect (USN)
and anosognosia for hemiplegia (AHP) measured with the Visual Analogue Test for Anosognosia for motor impairment (VATAm) and Unawareness of Motor and
Somatosensory (UMAS). USN severity was the mean of the results of the 5 neuropsychological tests. In (g) data are mean (SEM). In (a–f) and (h), the y-axis represents the %
severity of the deficit; lower is better. In (a) and (b), CoC is Center of Cancellation score.

stimulation [15]. However, in our case, we cannot confirm that
these deficits are due to independent mechanisms [1], but the
divergent improvement of USN and anosognosia suggests that
different treatments should be used for their rehabilitation.
Disclosure of interest
The authors declare that they have no competing interest.
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Alessio Facchina,b,c,*, Nicoletta Beschind
Department of Psychology, University of Milano-Bicocca, Piazza
dell’Ateneo Nuovo 1, 20126 Milano, Italy
b
Milan Centre for Neuroscience, 20126 Milano, Italy
c
Centre of Research in Optics and Optometry, University of MilanoBicocca (COMIB), 20126 Milano, Italy
d
Neuropsychological Service, Rehabilitation Department, A.S.S.T. Valle
Olona, 21100 Varese , Italy
a

*Corresponding author. Department of Psychology, University of
Milano-Bicocca, Piazza dell’Ateneo Nuovo 1, 20126, Milano, Italy
E-mail address: alessiopietro.facchin@gmail.com (A. Facchin).
Received 21 September 2017
Accepted 22 December 2017
Available online xxx

Please cite this article in press as: Facchin A, Beschin N. Different impact of prism adaptation rehabilitation in spatial neglect and
anosognosia for hemiplegia. Ann Phys Rehabil Med (2018), https://doi.org/10.1016/j.rehab.2017.12.007