Pure Amorphagnosia without Tactile Object Agnosia

Abstract

A 54-year-old female showed amorphagnosia without ahylognosia and tactile agnosia 40 days after the onset of right cerebral infarction. Her basic somatosensory functions were normal. The appreciation of substance qualities (hylognosia) was preserved, but the patient’s inability to recognize the size and shape (morphagnosia) was confined to 2- and 3-dimensional shapes (amorphagnosia) in the left hand. However, the patient’s ability to recognize real daily objects was well preserved. Brain MRI after admission showed ischemic lesions confined to the right pre- and postcentral gyri and the medial frontal cortex on DWI and FLAIR images. An analysis of SPECT images revealed that the most decreased areas were localized to the pre- and postcentral gyri, superior and inferior parietal lobules, supramarginal gyrus, and angular gyrus. Considering the previous reported cases, the responsible lesion for the impaired perception of hylognosia and morphagnosia may not necessarily be confined to the right hemisphere. To date, 5 reports (6 cases) of tactile agnosia have been published; 4 cases presented with both ahylognosia and amorphagnosia, while 1 presented with only amorphagnosia, and another showed amorphagnosia and mild ahylognosia. Our case is the first to present with only amorphagnosia without tactile agnosia. The mechanism for the well-preserved recognition of real objects may depend on the preserved hylognosia. Of note, there have been no reports showing only ahylognosia without amorphagnosia. Further studies are necessary to clarify whether or not patients with preserved hylognosia or morphagnosia retain the ability to perceive real objects.

Beta resting-state functional connectivity predicts tactile spatial acuity

“…2021 ). In the somatosensory process, lesions in the SPL can cause tactile agnosia, which is an inability to recognize objects through touch ( Kubota et al. 2017 ), suggesting that the SPL contributes to the perception of objects by touch ( Passarelli et al.…”

Unilateral tactile agnosia as an onset symptom of corticobasal syndrome

“…However, although agnosia has been extensively investigated for the visual modality and, to some extent, for the acoustic one (Vignolo et al, 1997;Simons and Lambon Ralph, 1999;Riddoch and Humphreys, 2003;Burns, 2004;Garrido et al, 2018;Miceli and Caccia, 2023), haptic recognition mechanisms are still poorly understood (Bottini et al, 1995;Bohlhalter et al, 2002). The difficulty in investigating tactile agnosia derives from the rarity of this disorder and the lack of consensus on both the semantic labelling, as different terms have been proposed to define the same impairment, and the adopted methods of investigation (Endo et al, 1992;Reed et al, 1996;Saetti et al, 1999;Kubota et al, 2017). For example, in the literature, the term "morphoagnosia" has been used to indicate a difficulty in shape and size discrimination, which does not necessarily preclude real object identification (Endo et al, 1992;Reed et al, 1996;Saetti et al, 1999;Kubota et al, 2017), distinct from "hyloagnosia, " i.e., the inability to discriminate object's qualities.…”

“…The difficulty in investigating tactile agnosia derives from the rarity of this disorder and the lack of consensus on both the semantic labelling, as different terms have been proposed to define the same impairment, and the adopted methods of investigation (Endo et al, 1992;Reed et al, 1996;Saetti et al, 1999;Kubota et al, 2017). For example, in the literature, the term "morphoagnosia" has been used to indicate a difficulty in shape and size discrimination, which does not necessarily preclude real object identification (Endo et al, 1992;Reed et al, 1996;Saetti et al, 1999;Kubota et al, 2017), distinct from "hyloagnosia, " i.e., the inability to discriminate object's qualities. Morphoagnosia together with hyloagnosia accounts for Lissauer's apperceptive level.…”

“…Morphoagnosia together with hyloagnosia accounts for Lissauer's apperceptive level. However, a double dissociation between hyloagnosia and morphoagnosia has never been reported, and the presence of morphoagnosia without hyloagnosia has been described only in two cases (Saetti et al, 1999;Kubota et al, 2017). The impairment in shape recognition has also been referred to as "astereognosis, " when the difficulty is secondary to an impairment in spatial discrimination (Carlson and Brooks, 2009).…”

“…Although tactile agnosia usually manifests on one hand (Platz, 1996;Reed et al, 1996;Valenza et al, 2001;Estañol et al, 2008;Hömke et al, 2009;Veronelli et al, 2014;Kubota et al, 2017), the brain damage may be also bilateral (Endo et al, 1992;Saetti et al, 1999).…”