Overview of Gerstmann Syndrome and Apraxia

Gerstmann syndrome is a rare neurological disorder that can arise due to brain injury or other developmental disorders and can be extremely debilitating to anyone suffering from the disorder. The nature of this syndrome is not genetic so there is no chance of passing it onto any offspring. Four key symptoms occur including, dysgraphia (an inability to write), acalculia (an inability to do maths), finger agnosia (inability to identify their own or another’s fingers) and left-right disorientation (inability to distinguish left from right). When all four of these symptoms appear together without any other mental disabilities it is known as pure Gerstmann's syndrome.¹

Like Gerstmann syndrome, apraxia is also a rare neurological disorder that can cause an affected individual to become unable to perform skilled movements. It has been shown to affect motor cognition, planning and task performance without disrupting basic motor functions, sensation or comprehension.² This means a person's understanding of a command is unaffected but they don’t possess the ability to carry it out, without the presence of any physical paralysis. There are multiple types of apraxia including limb-kinetic, ideomotor, conceptual, ideational, buccofacial, constructional and oculomotor.³

Both apraxia and Gerstmann syndrome are caused by brain abnormalities but the causes of each can differ. This causes the symptoms to differ too, where Gerstmann syndrome affects cognitive ability so the affected individual doesn’t understand commands. Whereas apraxia doesn’t affect the understanding the individual still can’t carry out the command. 

Gerstmann Syndrome

Gerstmann syndrome has a diagnostic criteria that consists of four cardinal symptoms including finger agnosia, left-right disorientation, dysgraphia and dyscalculia. Each symptom is tested differently.

• Finger agnosia - The physician will cover the patient's eyes and ask them to stretch out their fingers. The physician will then proceed to touch one of the fingers and ask the patient to identify which one it was. This test needs to be done with the patient's eyes open and closed to ensure accuracy and a 20% false recognition is needed for a positive diagnosis
• Left-right disorientation - The patient will be given an instruction, such as "Place your right hand on your left ear." A positive diagnosis is indicated if the patient is unable to correctly follow the instructions
• Dysgraphia - the physician will ask the patient to carry out multiple handwriting assessments for example writing out sentences
• Dyscalculia - The patient will be asked to solve mathematical equations both by working them out and in their head⁴

Gerstmann syndrome can be diagnosed in adults if all four of the symptoms are present and all other causes for the symptoms have been ruled out. It is harder to diagnose in children but is usually identified when they are in school and have difficulty in maths and distinguishing left from right. Constructional apraxia isn’t common among affected children.¹

It has been discovered that this syndrome is caused by brain lesions in the angular gyrus of the dominant hemisphere (this is usually the left). Damage is also found in neighbouring structures like the parietal, temporal, and occipital lobes. These brain lesions can arise due to strokes, tumours, aneurysms, alcoholism, carbon monoxide poisoning and anaphylactic shock.⁴

When a patient displays symptoms of Gerstmann syndrome the physician may decide to carry out scans. MRI may be used to find abnormalities such as lesions in the parietal lobe, whilst CT scans can be used to find obstructions in blood flow. Both of these scans are used to identify brain injury associated with Gerstmann syndrome. If the patient is positively diagnosed, abnormalities may have been discovered in the angular gyrus region of the brain, however, the nature of the abnormalities may differ for each patient.⁴

If a patient is positive for Gerstmann syndrome occupational and speech therapies may be recommended. There is currently no cure but surgery may be able to help with some of the causes of the syndrome such as brain injuries. In adults, symptoms may disappear over time, but in children, this is not the case, however, they usually learn to adjust to the symptoms. Calculators and word processors may help children who are struggling in school. Intensive speech therapy has also been shown to have massive improvements in children when diagnosed early.⁴

Apraxia

There are multiple types of apraxia which include: 

• Limb-kinetic apraxia: an individual cannot make precise movements with their limbs (fingers, arms or legs). For example, an affected individual can’t use scissors even if they’ve done it correctly in the past
• Ideomotor apraxia: an individual can’t perform or copy gestures, for example, head movements like nodding
• Ideational apraxia: an individual can’t carry out a sequence of specific movements, for example making coffee
• Buccofacial apraxia: an individual can’t coordinate specific facial movements, for example whistling 
• Constructional apraxia: an individual can’t draw or copy simple diagrams
• Oculomotor apraxia: an individual has difficulty moving their eyes³ 
• Verbal apraxia - an individual is unable to correctly move their tongue or lips so words are not pronounced correctly⁷

Like Gerstmann syndrome, apraxia is also caused by lesions in the frontal lobe of the brain (specifically the parietal lobe of the left hemisphere). This is the structure in the brain that stores learned patterns and movements, so an affected individual would be unable to retrieve them. Lesions are also found in other parts of the brain such as the premotor cortex.³ These brain damages could be the result of strokes, neurodegenerative diseases (e.g. Alzheimer's and Huntington's disease), schizophrenia, tumours and brain injury.²

Physical and neuropsychological testing is used to identify apraxia when a patient displays symptoms of the disorder. If a person is tested positive, additional testing is required to identify the causes. This testing can include fMRI and PET scans to identify the brain lesions causing the apraxia.²

Once the disorder and its potential causes are identified, the patient may be recommended for rehabilitation through speech, occupational, and physical therapy.  The disorder is also managed by addressing the underlying disorder, so if it’s caused by brain damage, surgery may be required. Right now there is no widely accepted treatment for apraxia however new technologies are being explored such as transcranial magnetic stimulation.²

The intersection of Gerstmann Syndrome and Apraxia

Gerstmann syndrome and apraxia have a lot of similarities including affected brain regions and similar symptoms. This can make it difficult to differentiate between the two and gain an accurate diagnosis. As both of these disorders are extremely rare, it is difficult to further research. 

Research and Advances

There have been many research advances in improving treatments for both Gerstmann syndrome and apraxia. Steroids have been proven to complicate Gerstmann syndrome instead of improving symptoms. It has also been found that Natalizumab (a monoclonal anti-integrin antibody) has been useful in managing Gerstmann syndrome. However, deep brain stimulation (DBS) has been thought to have a lot of promise when treating Gerstmann syndrome. This is because DBS has shown great improvements when treating Parkinson’s disease which has a similar pathophysiology to Gerstmann syndrome. Currently, there are no case reports of treating Gerstmann syndrome with DBS and it is not a field that has been explored enough.⁵

Apraxia also requires more research in the future but due to the rarity of the disorder, it is difficult to research. Ultrasound biofeedback treatments have been tested to see the positive effect on verbal apraxia. This is where an affected child undergoes speech-motor practice with tongue position and movement. The tests performed have had positive results, proving this method to be a viable option in the future as it develops.⁶ Genetic factors are also being researched to determine their relationship with the disorder, along with studies focusing on the specific areas of the brain.⁷ 

Conclusion

To conclude, Gerstmann syndrome and apraxia are rare neurological disorders caused by lesions in the brain (specifically the parietal lobe). Both disorders cause similar symptoms, making it extremely challenging to differentiate between them during diagnosis. Treatments specific to the disorders are also not very thoroughly researched due to the rarity however it is known that early discovery and treatment can significantly improve results in children. With further research, tailored treatments may also be discovered which is vital when trying to alleviate the direct cause of symptoms. Research is also important for pinpointing where the disorders manifest allowing the further development of tailored treatments.