Gerstmann Syndrome

Gerstmann syndrome refers to a constellation of four neurologic deficits: agraphia, acalculia, finger agnosia , and left-right disorientation. All symptoms must be present for a diagnosis of true Gerstmann syndrome.

Gerstmann Syndrome Nicholas Bontrager 2; Padmaja Sudhakar 1,2, MD Department of Neurology (1) and Ophthalmology(2) University of Kentucky Overview • Gerstmann syndrome refers to a constellation of four neurologic deficits: agraphia, acalculia, finger agnosia , and left-right disorientation. • All symptoms must be present for a diagnosis of true Gerstmann syndrome. • Commonly associated with damage to the dominant posterior parietal lobe, where tracts related to these functions are located. • The angular gyrus and adjacent structures (at the confluence of parietal, temporal and occipital lobes) are affected. • Rarely non dominant right hemisphere may be involved. • Some studies show that it may occur from involvement of the left middle frontal lobe of the dominant hemisphere. Characterizing symptoms The following symptoms must be present together for a true diagnosis • Agraphia: Inability to write spontaneously and write from dictation; ability to copy written text is preserved. • Acalculia: Inability to perform mental and written calculations with single and especially multiple digit numbers. • Finger agnosia: Inability to distinguish between fingers. Difficulty with naming and distinguishing fingers, as well as following commands related to specific fingers. • Left-right disorientation: Confusing left and right sides of patient’s/examiner’s body, not due confusion with the concept of left and right or verbal impairment. Etiology • Underlying etiology has been debated over the years since Gerstmann syndrome was first described in Gerstmann’s case report in 1924. • There has been continued intrigue about the common denominator of the seemingly unrelated manifestations. • Current favored mechanism is that the specific tetrad of symptoms seen in Gerstmann syndrome arises from a disconnect in the neuronal fiber tracts that carry signals for the four separate neurologic functions that are impaired. • According to this theory, symptoms arise together through anatomical connection rather than a common functional impairment -a precisely localized disconnect of four tracts occurs at the posterior parietal lobe to create the constellation of symptoms. • The disconnect can occur from a variety of underlying causes, including stroke, tumor, aneurysm, etc. Common additional symptoms • Other symptoms and signs which may accompany this syndrome differ according to the cause of this syndrome such as; apraxia[34], optic ataxia[39], cognitive decline[19], numbness or weakness.[11] Gesture imitation defects and toe agnosia (seen as an association with finger agnosia so it may be named as digit agnosia[40]) • Case report described an alternating visual-spatial processing issue in the form of “vision like swiss cheese” along with normal left-right disorientation. • Aphasia is commonly described which can make thorough examination and diagnosis difficult. Work up • A thorough examination is required to characterize Gerstmann syndrome. • Exam should determine if other sensory, motor, and cognitive deficits are present that may influence results, as this may affect diagnostic accuracy. • Exam should especially focus on the angular gyrus of the dominant parietal lobe. • MRI head with and without contrast is the preferred first step for assessing for intracranial lesions causing Gerstmann syndrome. https://pubmed.ncbi.nlm.nih.gov/29519471/ Examination: Agraphia • Patients are commonly able to copy text adequately but are unable to transcribe spoken words or pictures into written words. Therefore, examination should focus on a patient’s ability to do the latter tasks. • Example 1: Patient is shown a picture of a clock and asked to write what it is. • Example 2: Patient is given the phrase “He shouted the warning,” and is asked to repeat it, explain the meaning, and write it down. (Most difficult test for many patients.) • In addition to the examples, it is important to assess a patient’s ability to write spontaneously and to write things dictated to them. Examination: Acalculia • Patients have difficulty with performing mental and written calculations with single and especially multidigit numbers. • Testing should assess ability to solve verbal and written arithmetic problems. • Example 1: Examiner shows patient a written math problem (e.g. “43 - 24”) on a card and asks patient to copy it and solve it. • Example 2: Patient is required to multiply a double-digit number by a single-digit number (e.g. “24 x 3”) without seeing the numbers written down. Examination: Finger agnosia • Patients will mainly have difficulty naming digits when they are out of sight. • Patients have more difficulty with naming middle 3 fingers than they do with naming 1st and 5th digit. • Examination should use nonverbal tests alongside verbal tests to distinguish between finger agnosia (unable to recognize fingers by using senses) and finger anomia (unable to remember names of fingers). • Example 1: “Two-point finger test.” Examiner touches fingers of patient at two different positions on one hand and patient determines if examiner touched the same finger or different fingers, while hand is out of sight. • Example 2: Patient holds both hands behind back. Examiner touches a finger of one hand, and patient must respond by moving corresponding finger of the other hand. Examination: Right-left disorientation • Patients may be able to follow one-stage right vs left commands (e.g. wave your right hand) by remember features of their body unique to one side. • Therefore, examination should focus on distinguishing right vs left on the examiner’s body or using two-stage right vs left commands (eg point with your right hand to examiner’s right hand) • Example: Combine the two-stage and examiner-focused techniques by having patient use right hand to point to examiner’s left shoulder. • Follow-up with variations such as patient’s right hand pointing to examiner’s right ankle, etc. Causes of Gerstmann syndrome • Anything that creates a focal disruption in the neuronal tracts in the dominant posterior parietal lobe, particularly within the angulate gyrus. • Common causes of disruption include tumor, ischemic stroke, cortical atrophy, aneurysm, multiple sclerosis. • Partial epilepsy of parietal lobe may cause this syndrome as an ictal symptom. • Diffuse toxicity to brain parenchyma such as carbon monoxide poisoning can cause Gerstmann syndrome. Treatment • Some causes of Gerstmann syndrome are reversible, and treatment for these involves fixing the underlying cause. • This could include tumor excision; multiple sclerosis treatment; removal of toxic stimuli; epilepsy treatment . • Cases of Gerstmann syndrome have been shown to respond well to intensive rehabilitation treatment. References https://eyewiki.aao.org/Gerstmann_Syndrome#cite_note-:0-6 https://pubmed.ncbi.nlm.nih.gov/29519471/ https://www.aaopt.org/detail/knowledge-base-article/cerebral-visual-impairment-effective-rehabilitation-for-the-vision-consequences-ofgerstmann-syndrome https://www.ncbi.nlm.nih.gov/pmc/articles/PMC495679/ https://www.ncbi.nlm.nih.gov/books/NBK519528/ [Will organize more thoroughly]