Introduction

Gerstmann syndrome is a rare neurological disorder caused by brain damage in a specific area, mostly the left hemisphere of the parietal lobe in the angular gyrus region.¹

It may occur after tumours or strokes. It consists of four primary symptoms:^1,2

• Inability to calculate (acalculia)
• Inability to identify their fingers (finger agnosia)
• Difficulty in distinguishing left from right
• Writing disability (agraphia)

What is agraphia?

Agraphia is the loss of ability to write due to damage in the parietal lobe of the brain, particularly in the region responsible for integrating motor skills and cognitive processes necessary for writing. Unlike other forms of agraphia caused by broader cognitive decline or motor deficits, the agraphia seen in Gerstmann syndrome is closely linked to specific disconnections in the brain's ability to coordinate visual, spatial, and language skills.²

Understanding agraphia in Gerstmann syndrome is necessary because it disrupts both written communication and reflects the broader cognitive challenges faced by individuals with this condition. Addressing agraphia through targeted therapies can significantly improve the quality of life for patients, making it a central focus in managing the syndrome.²

Understanding agraphia

Types of agraphia

An inability to write, or agraphia, often occurs on its own, but it also can be found with other nervous system disorders such as alexia, apraxia, or hemispatial neglect. Agraphia can be classified into two groups – central agraphia and peripheral agraphia.³

Central agraphia

The process of writing starts with individuals gathering a letter or a group of letters to make up a single sound and then communicating information. To write properly, a person must know alphabetical letters and then organise the letters to produce proper words and create grammatically correct sentences. Central agraphia results in the disruption of these processes.³

Peripheral agraphia

To write correctly, an individual must coordinate movements to draw out letters (praxis), mentally organise letters into words (motor programming), use visuospatial skills to guide a writing instrument on a surface and rely on the motor system to execute these tasks. Peripheral agraphia can lead to an impairment in motor planning or action. This type of agraphia may still involve the central nervous system, such as when a motor cortex lesion causes paresis in the writing hand, despite not directly affecting linguistic centres.³  

Specific characteristics of agraphia in Gerstmann syndrome

Agraphia in Gerstmann syndrome results from damage to the posterior lobule of the dominant parietal lobe in the area of the angular gyrus, which is considered central agraphia. These areas are responsible for integrating visual, spatial, and language skills necessary for writing. This can help distinguish the symptoms of agraphia in Gerstmann syndrome from peripheral agraphia, which involves impairments in motor function.⁴

Neurological basis

Brain regions associated with writing skills

Writing is a complex cognitive and motor task that involves several brain areas. The primary areas associated with writing skills include:^4,5

• Angular Gyrus: the angular gyrus, located in the parietal lobe, is essential for processing language and integrating information. It is related to the cognitive processing of language or word comprehension, which is essential for communication
• Supramarginal Gyrus: located near the angular gyrus, it assists in the process of writing
• Broca’s Area: it is associated with speech comprehension and production. It assists in sequencing letters and words and ensuring grammatical structure
• Primary Motor Cortex: The motor cortex is responsible for controlling voluntary movements, such as holding a pen on a writing surface without moving. It is essential for the writing execution because writing engages both sensory and motor areas
• Exner’s Area: Exner’s area is activated during writing and is specifically involved in motor planning for writing. It works with other areas to organise the hand and finger movements

The link between brain damage and agraphia in gerstmann syndrome

In Gerstmann syndrome, agraphia occurs due to damage primarily in the dominant parietal lobe, especially the angular gyrus. This region is responsible for processing the skills required for writing. When this area is damaged, the individual may lose the ability to form letters or words, but the motor function of their hands is still functioning.^4,5

Damage to the angular gyrus is central to agraphia in Gerstmann syndrome. Because the angular gyrus facilitates the translation of visual and spatial information into motor commands, lesions in this region disrupt the ability to organise and produce written text. This results in central agraphia, where the issue lies in the cognitive processing necessary for writing rather than a purely motor deficit. The angular gyrus also integrates visual stimuli with language, making it difficult for patients to recognise and reproduce written symbols.

Clinical features of agraphia in gerstmann syndrome

Symptoms and presentation 

As mentioned above, writing problems in this condition can take different forms, and the symptoms depend on the brain areas affected. However, agraphia in Gerstmann syndrome can be classified into 2 types – aphasic agraphia (related to language processing) and apraxic agraphia (related to motor planning). Patients with Gerstmann syndrome struggle with various writing challenges. One common issue is the inability to form letters correctly and keep writing in a straight line. This often results in abnormal writing that is hard to read. These problems occur because the brain has trouble processing the motor and spatial information needed to write. Another difficulty involves spelling and organising letters. Patients may mix up the order of letters in words or leave out letters altogether. Some patients also have trouble copying letters or words.⁶

Examples of writing errors typical in gerstmann syndrome

Patients often make specific types of mistakes when writing. Those with aphasic agraphia tend to misspell words, substitute letters, or leave out letters entirely. In more severe cases, their writing may become a disorganisation of letters that do not form meaningful words. For example, they may write random letters that make no sense, a condition called jargon agraphia.

In apraxic agraphia, the problem is more about the placement of letters. These patients might scatter letters across the page in the wrong order or have trouble keeping their writing within the lines. For example, they may attempt to write ‘house’ but the letters might be misplaced or look disorganised. In extreme cases, some patients are unable to write even a single letter, which is called absolute agraphia.

Patients who develop Gerstmann syndrome make errors in letter order, which means that the letters that form a word are mixed up (for example ‘house’ becomes ‘uohse’). It differs from other types of writing disorders, in which extra letters or completely wrong letters might be performed.

Associated cognitive impairments

Relationship to other symptoms of gerstmann syndrome

The symptoms of Gerstmann syndrome, like trouble with calculation (acalculia) and difficulty recognising fingers (finger agnosia), are often linked and related to cognitive function.⁶ These issues result from damage in the same part of the brain. An inability to recognise a specific finger is one of the tasks requiring cognitive capacity because it needs to stimulate neuron cells and then translate to visual terms to localise the finger. Some patients may show an inability to understand or read numbers, which is similar to the inability to calculate. These findings show that patients lose control over voluntary bodily functions. The different symptoms work together and affect how the brain handles these types of tasks.⁶

Impact on overall cognitive function

The thinking problems caused by Gerstmann syndrome, such as struggles with calculation and recognising fingers, can affect overall brain function. These issues show that the brain’s ability to understand space, manage simple tasks, and even communicate does not function properly. Since these difficulties affect many areas of thinking, they may lead to bigger challenges, such as learning and retaining information.⁶

Diagnosis

Diagnostic criteria for gerstmann syndrome

To detect Gerstmann syndrome, the doctor will inquire about family history and perform a physical examination, in particular, a special neuron system examination to detect four characteristic symptoms including finger agnosia, right-left disorientation, dysgraphia, and dyscalculia. Patients who have these symptoms will be assessed by MRI/CT scans.⁷ Some damage in the dominant angular gyrus should be found with or without affecting the surrounding areas.

How agraphia contributes to the diagnosis

In agraphia, a special examination will be done. For example, the doctor will show the patient a picture of a clock and ask them to write down the word for it without saying it. Then, the doctor should show the patient the word ‘SEVEN’, and after the patient reads it and says it, they will be asked to write it down. Then, the doctor will ask the patient to repeat the sentence ‘He shouted the warning’, explain what it means, and write it.¹

Clinical assessments used to identify agraphia

To identify writing difficulties (agraphia), doctors often start with a simple bedside test to see how the patient is struggling with writing. If the results are unclear, more detailed tests can be done. Special tests like the Western Aphasia Battery or the Boston Diagnostic Aphasia Exam, usually given by a speech and language expert, can give a clearer picture of the problem and track how severe it is.⁸ A neuropsychologist may also give these tests as part of a full mental evaluation.

Management and treatment

Some causes of Gerstmann syndrome can be reversed and treated, such as by removing a tumour, stopping a haemorrhage, or addressing an epilepsy-related lesion.^9,10,11

Proper treatment for agraphia in Gerstmann syndrome depends on identifying the cause and location. Speech and language therapy, along with occupational therapy, are key treatments for writing difficulties. Sometimes, a combination of therapy, medication, or even surgery is needed.

It is also important to treat the cause of agraphia to prevent it from getting worse. If a tumour is causing issues in writing, treatments like chemotherapy, radiation, or surgery may be needed.³

Summary

Agraphia in Gerstmann syndrome is a writing disorder caused by damage to the angular gyrus in the brain’s dominant parietal lobe. It affects the brain’s ability to integrate visual, spatial, and language skills, leading to difficulties in forming letters, organising words, and maintaining correct letter order. Agraphia in this syndrome often occurs alongside acalculia, finger agnosia, and left-right disorientation. Diagnosis involves specialised tests, and key treatment includes speech and occupational therapy, with possible medical or surgical interventions based on the underlying cause.