Functional Neuroanatomy of Gerstmann Syndrome

Abstract & Commentary

By John J. Caronna, MD, Professor of Clinical Neurology, Weill Cornell Medical College. Dr. Caronna reports no financial relationships relevant to this field of study.

Synopsis: Gerstmann Syndrome is associated with lesions of the parietal cortex and subcortical white matter in the region of the angular gyrus. It should be considered one of the "disconnection" syndromes.

Source: Rusconi E, et al. A disconnection account of Gerstmann syndrome: Functional neuroanatomy evidence. Ann Neurol 2009;66:654-662.

From 1924 to 1930 in vienna, Josef Gerstmann published three case reports describing patients with finger-agnosia, dysgraphia, dyscalculia, and right-left disorientation. He asserted that these four symptoms constituted an independent syndrome and were the expression of disease in the left angular gyrus where, he postulated, there was a common functional denominator essential to these four cognitive faculties.

Since Gerstmann's description, authors who have studied the clinico-anatomic correlations of the syndrome found that the lesions, although always in the dominant hemisphere, were not restricted to the angular gyrus, and that the four components of Gerstmann syndrome usually were not an autonomous entity but part of many concurrent deficits including impaired recent memory, visual field defects, aphasia, and emotional lability.1

Based on the failure of intraoperative electrostimulation to identify a single site where disruptive stimulation would elicit all four symptoms,2 the current view is that there is no functional association of the four domains that fail in Gerstmann syndrome.

The present authors also sought to determine whether a shared cortical site existed that could account for a pure Gerstmann syndrome. They used functional magnetic resonance imaging (fMRI) in five healthy, right-handed subjects (four men, one woman, mean age 21 years) to study cortical activation patterns during each of the four tasks: calculation, left-right orientation, finger gnosis, and writing. Each task was repeated in two separate sessions for a total of eight sessions per subject.

None of the subjects showed parietal overlap of cortical activation patterns from the four cognitive domains. The authors then applied fiber tracking to diffusion tensor images to determine that parietal activation patterns across all four domains connected to a small region of subcortical parietal white matter at a location congruent with the subangular gyrus lesion in a reported case of pure Gerstmann syndrome.3

The authors postulate that Gerstmann's triad of symptoms arises from intraparietal disconnection after damage to a focal region of subcortical white matter.

Commentary

Gerstmann thought the syndrome he described was a disorder of the body schema restricted to the hand and fingers. Detailed neuropsychological testing in a patient with pure Gerstmann syndrome indicates that the impairment is attributable to disorders of a spatial nature.3 Mayer and colleagues studied their patient with MRI and cognitive testing. MRI showed a focal ischemic lesion located subcortically in the inferior part of the left angular gyrus and involving callosal fibers. The cortical layers were spared. Cognitive testing excluded language, praxis, memory, and intelligence disorders. The Gerstmann tetrad was associated with impaired ability to perform tasks necessitating mental rotation. On the basis of the report of Mayer and associates, it seems legitimate to consider the Gerstmann tetrad a true syndrome.

The report of Rusconi and colleagues supports the prevailing view that the cognitive functions impaired in Gerstmann syndrome do not share a common neuronal network and that their occurrence in cases of parietal lobe injury is due to anatomical proximity. The fiber tracts subserving the Gerstmann tetrad of cognitive functions are separate but co-localized in the subcortical white matter of the parietal lobe. Therefore, a purely subcortical lesion could produce the "cortical" deficits of Gerstmann syndrome by disconnection. A classical disconnection syndrome of alexia without agraphia has been reported in a patient with multiple sclerosis.4

References

1. Critchley M. The enigma of Gerstmann's syndrome. Brain 1966;89:183-198.

2. Roux FE, et al. Writing, calculating, and finger recognition in the region of the angular gyrus: A cortical stimulation study of Gerstmann syndrome. J Neurosurg 2003;99:716-727.

3. Mayer E, et al. A pure case of Gerstmann syndrome with a subangular lesion. Brain 1999;122:1007-1020.

4. Dogulu CF, et al. Alexia without agraphia in multiple sclerosis. J Neurol Neurosurg Psy 1996;61:528.