Gerstmann's Syndrome

Synonyms: Developmental Gerstmann syndrome (when it occurs in children), Gerstmann tetrad

The condition should not be confused with Gerstmann-Sträussler syndrome or Gerstmann-Sträussler-Scheinker syndrome - a transmissible spongiform encephalopathy.

This is a condition arising as a result of disease of the dominant parietal lobe at the angular gyrus.¹ Possibly both superior and inferior lobes need to be affected.² The specific effect of lesions of various lobes is discussed in the article on Space Occupying Lesions but in Gerstmann's syndrome in particular, the result is characterised by 4 components:

• Agraphia or dysgraphia
• Acalculia or dyscalculia
• Finger agnosia
• Left-right disorientation

Pure Gerstmann syndrome is said to be without aphasia. It generally presents as either a congenital or learning disorder or as a feature of a stroke of the middle cerebral artery. Both forms are rare, especially the childhood form. It can also be a feature of neurodegenerative diseases such as Alzheimer's disease or as a result of head injury.

The childhood type may occur in those with brain damage or in isolation with otherwise good mental function; the pathophysiology in children is not understood.³ It does not seem to have a genetic component and is not listed in OMIM. It has been argued that developmental Gerstmann's syndrome is not a unique entity but a feature of other neurodevelopmental disorders.⁴ This has also been disputed.⁵ In adults, the risk factors appear to be the same as those for a cerebrovascular event.

There is loss or absence of four sensory abilities.

• Loss of the ability to express thoughts in writing (agraphia, dysgraphia)
• Inability to perform simple arithmetic calculations (acalculia)
• Inability to recognise or indicate one's own or another's fingers (finger agnosia)
• Inability to distinguish between right and left

In addition, many adults also experience aphasia, (difficulty in expression with speech, in understanding speech or in reading and writing).

The speech area is in the dominant hemisphere that is on the left in over 95% of right handed people. It is also on the left in 75% of left handed people but in the other 25% it appears to be bilateral.

Most paediatric cases are identified when children start school and they are challenged with writing and numbers. Generally, children with the disorder exhibit poor handwriting and spelling and difficulty with mathematical functions (adding, subtracting, multiplying and dividing). An inability to differentiate right from left and to discriminate among individual fingers may also be apparent. In addition to the four primary symptoms, many children also suffer from constructional apraxia, an inability to copy simple drawings. Frequently, there is also impairment in reading (dyslexia). Children with good intellectual function as well as those with brain damage may be affected.

Eliciting features of Gerstmann's syndrome

1. Agraphia
   • Illegible or very poor writing
   • Inconsistencies in forming letters
   • Mixture of upper and lower case letters or print and cursory writing
   • Irregular letter sizes and shapes
   • Unfinished letters
   They struggle to use writing for communication.
2. Acalculia
   This is tested by asking the patient to do serial subtraction of 7 from 100. This means 100, 93, 86, 79, 72, etc. It must be interpreted in the light of the educational level of the patient including the age of a child. An easier test may be applicable, especially for children.
3. Finger agnosia
   Finger agnosia is difficulty in distinguishing fingers on the hand. It is tested by asking questions like, "Touch my index finger with your index finger" and "Touch your nose with your little finger."
4. Left-right disorientation
   This is confusion of the right and left limbs and indicates a lesion in the dominant parietal lobe. It is tested by questions like, "Show me your left hand. Touch your right foot" and "Touch your left ear with your right hand." A positive test is the inability to obey these commands in the presence of otherwise normal sensory and motor function.

In adults, differential diagnosis is that of stroke and includes dementia.⁶ In children, it is with more global brain damage and learning difficulties.

MRI scan will usually show a lesion of the angular gyrus in the left parietal lobe.

As well as occurring in strokes, head injuries and developmental disorders, the syndrome has been associated with cerebral atrophy, alcoholism, carbon monoxide poisoning, lead poisoning, anaphylactic shock and systemic lupus erythematosis.⁷

There is no cure for Gerstmann's syndrome. Treatment is symptomatic and supportive. Occupational and speech therapies may help diminish the dysgraphia and apraxia. There has been a recognition of the association between finger recognition and numerosity and recently, there has been promising work done where improving finger gnosis through training exercises has led to improvements in the mathematical skills of young children.⁹ Calculators and word processors may also help school children cope with the symptoms of the disorder.

In adults, many of the symptoms diminish with time. Although it has been suggested that in children symptoms may diminish over time, it appears likely that most children probably do not overcome their deficits but learn to adjust to them. It has been suggested that early diagnosis and intensive treatment gives better outcome.⁴