Gerstmann Syndrome

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 by M. Tariq Bhatti, MD on June 7, 2023.


Gerstmann syndrome is a neuropsychological disorder characterized by the tetrad of agraphia (inability to write), acalculia (inability to perform mathematical calculations), finger agnosia (inability to name, discriminate, or identify fingers), and left-right disorientation (inability to distinguish left from right). It was first described by Joseph Gerstmann in a 1924 case study of a 52-year-old woman who had a left-sided stroke presenting with the four cardinal signs, with some subsequent case reports reporting additional cognitive deficits.[1] Despite its recognition in the neurological literature, most knowledge has been described in case studies, and scant epidemiological data is available.[2]

Localization and Etiology

The classically described location for the lesion is the dominant parietal lobe, which is typically on the left side in right-handed individuals. Specifically, the angular gyrus (Brodmann area 39) has been implicated in many studies, and thus this condition is sometimes referred to as angular gyrus syndrome.[3] Connections to the inferior frontal lobe have also been reported. It is debated whether Gerstmann syndrome constitutes a distinct clinical entity with a specific neuroanatomical correlation.[4] Critics argue that many reported cases lack all four of the cardinal signs or include extra deficits (aphasia, alexia, and perceptual disorders). Attempts to recreate Gerstmann syndrome via electrical stimulation of the brain have only been successful by targeting multiple brain regions simultaneously.[5]

Etiologies for Gerstmann syndrome include focal lesions from:
  • Ischemic stroke
  • Tumors
  • Aneurysm (carotid artery or middle cerebral artery)
  • Progressive multifocal leukoencephalopathy
  • Multiple sclerosis
  • Cortical atrophy
Diffuse toxicities implicated in causing Gerstmann syndrome include:
  • Alcohol
  • Carbon monoxide
  • Lead

Transient Gerstmann syndrome has been reported in parietal lobe epilepsy. There are also cases of iatrogenic Gerstmann syndrome resulting from cerebral angiography.[6]

Developmental Gerstmann syndrome (DGS) has been reported in children as a type of learning disorder. The cause of DGS is unknown, but children who have it are thought to have brain damage. DGS is usually identified in school-age children that exhibit difficulty with writing or calculating. These children tend to also suffer from constructional apraxia (inability to copy simple drawings). [7]

Components of Gerstmann Syndrome

Finger agnosia is the inability to name, move, or touch specific fingers identified by the examiner. It is bilateral, worse with the three central fingers, and can include the toes (in which case it is known as digit agnosia). Visual loss exacerbates the disability. The agnosia may also apply to the examiner’s fingers or images of fingers.

Left-right disorientation is the inability to differentiate between the left and right side of one’s own body or that of the examiner. It is best tested by instructing the patient to point with a specific hand to a specific shoulder on the examiner (“Point to my left shoulder with your right hand”). The patient has no difficulty distinguishing between front/back or up/down.

Agraphia is the inability to write with the hand what one wants to or is told to write. The ability to copy text and spell correctly is preserved. There is evidence that the underlying issue involves motor planning and is thus a form of apraxia.

Acalculia is the inability to solve math problems, either verbally or written. It is the most variable and least understood aspect of Gerstmann syndrome. It is strongly associated with semantic aphasia, which is difficulty understanding words with spatial connotations, such as “above” or “below.”


Evaluation for Gerstmann syndrome begins with confirmation of the clinical findings.

Finger agnosia can be tested by:
  • Covering the patient's eyes, touching one of their fingers, and having them report which finger was touched.
  • Two-point finger test: covering the patient’s eyes, touching their fingers in two spots (either on one finger or on different fingers), and having them report if one or two fingers were touched.
  • Homologous finger test: a finger on one hand is briefly touched by the examiner, and the patient is asked to move the homologous finger on the other hand.
  • Finger strip test: ask the patient to arrange five strips of paper labelled with the names of the five fingers in the correct order that they would appear on the hand.
  • Perform verbal and nonverbal testing to distinguish finger agnosia from finger anomia.
Left-right disorientation can be tested by:
  • Giving the patient written instructions to touch their left ear with their right hand or vice versa, having them read aloud and explain the instruction, and then having them perform it.
  • Verbally instruct the patient if they are unable to read aloud and explain the written instructions.
  • It is important to use two-stage commands when testing for left-right disorientation.
Agraphia can be tested by:
  • Showing the patient an image of a clock and having them write what it is.
  • Showing the patient the word “seven” and having them say it aloud and write it.
  • Saying to the patient the sentence “He shouted the warning” and having them repeat it back to you, explain it, and write it.
  • It is important to test the patient’s ability to write spontaneously and to write what is dictated to them.
Acalculia can be tested by:
  • Giving the patient written math equations (e.g. “85-27”) and having them calculate and write the answer.
  • Verbally giving the patient a multiplication question and having them mentally calculate and report the answer.

Labs and Imaging

Suspected Gerstmann syndrome should be investigated with neuroimaging. Magnetic resonance imaging (MRI) is the preferred first step to identify a structural lesion. Imaging should focus on the dominant parietal lobe, particularly the angular gyrus. Evidence of infarction would appear as abnormally reduced diffusivity on acute phase MRI. Computed tomography (CT) is also a valid option if imaging is needed more emergently and would show an infarction as a low-density focus. Other helpful testing may include angiography to evaluate for middle cerebral artery stenosis, positron emission tomography (PET) scan to detect decreased cerebral blood flow, and electroencephalography (EEG) to look for slow waves.[6]


Gerstmann syndrome is incurable, and treatment revolves around managing symptoms and providing support. Occupational and speech therapy are helpful in limiting disability severity. Modern technology such as calculators and word-processing software can alleviate disease burden.[8]


There is limited evidence that suggests adults with Gerstmann syndrome may improve slightly over time. Children with developmental Gerstmann syndrome may not have as favorable a prognosis. It is unclear whether patients experience true improvement or merely compensate for their disability. Early detection and intervention are crucial for prognosis in children.


See Also:

Alexia without Agraphia

  1. Rusconi E, Pinel P, Dehaene S, Kleinschmidt A. The enigma of Gerstmann's syndrome revisited: a telling tale of the vicissitudes of neuropsychology. Brain. 2010 Feb;133(Pt 2):320-32. doi: 10.1093/brain/awp281. Epub 2009 Nov 10. PMID: 19903731.
  2. Ardila A. Gerstmann Syndrome. Curr Neurol Neurosci Rep. 2020 Aug 27;20(11):48. doi: 10.1007/s11910-020-01069-9. PMID: 32852667.
  3. Rusconi E. Gerstmann syndrome: historic and current perspectives. Handb Clin Neurol. 2018;151:395-411. doi: 10.1016/B978-0-444-63622-5.00020-6. PMID: 29519471.
  4. Rusconi E. Gerstmann syndrome: historic and current perspectives. Handb Clin Neurol. 2018;151:395-411. doi: 10.1016/B978-0-444-63622-5.00020-6. PMID: 29519471.
  5. Rusconi E, Pinel P, Dehaene S, Kleinschmidt A. The enigma of Gerstmann's syndrome revisited: a telling tale of the vicissitudes of neuropsychology. Brain. 2010 Feb;133(Pt 2):320-32. doi: 10.1093/brain/awp281. Epub 2009 Nov 10. PMID: 19903731.
  6. 6.0 6.1 Altabakhi IW, Liang JW. Gerstmann Syndrome. [Updated 2021 Jul 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:
  7. PeBenito R, Fisch CB, Fisch ML. Developmental Gerstmann's syndrome. Arch Neurol. 1988 Sep;45(9):977-82. doi: 10.1001/archneur.1988.00520330063011. PMID: 3415528.
  8. Gerstmann Syndrome Information Page. The National Institute of Neurological Disorders and Stroke. Last Updated March 27, 2019. Accessed September 26, 2021.
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