What is the condition that causes micrographia (small handwriting)?

From the Guidelines

Parkinson's disease is the primary condition that causes micrographia, characterized by abnormally small, cramped handwriting. This symptom occurs due to the degeneration of dopamine-producing neurons in the brain, particularly in the substantia nigra, which affects motor control and coordination, as discussed in the context of movement disorders and neurodegenerative diseases 1. The reduced dopamine levels lead to the cardinal motor symptoms of Parkinson's, including rigidity, bradykinesia (slowness of movement), and tremor, which collectively contribute to micrographia.

Some key points to consider in the diagnosis and management of micrographia include:

• The importance of structural imaging, with MRI preferred over CT, to look for patterns of atrophy, parenchymal abnormality, or abnormal substance deposition, and to exclude other potential etiologies 1.
• The use of more advanced MRI techniques, such as diffusion tensor imaging, magnetization transfer ratio imaging, and postprocessing techniques like quantitative volumetric analysis, to evaluate the microstructural makeup of the brain parenchyma 1.
• The role of nuclear medicine studies in evaluating for abnormal patterns of glucose metabolism, buildup of abnormal particles or proteins within neurons, dysfunction or loss of specific categories of neurons, or individual neurochemical deficits 1.
• The treatment of underlying Parkinson's disease with dopaminergic medications, such as levodopa-carbidopa, dopamine agonists, or MAO-B inhibitors, and the potential benefits of physical and occupational therapy focusing on hand exercises and using adaptive writing tools with larger grips to manage micrographia symptoms.

Early recognition of micrographia is crucial as it can sometimes be one of the earliest signs of Parkinson's disease, appearing before more obvious motor symptoms develop, highlighting the need for a comprehensive diagnostic approach that considers the complex features of movement disorders and neurodegenerative diseases 1.

From the Research

Condition that Causes Micrographia

• Micrographia is a common symptom in Parkinson's disease, which manifests as either a consistent or progressive reduction in the size of handwriting or both 2.
• The condition is associated with decreased activity and connectivity in the basal ganglia motor circuit, and dysfunction of the basal ganglia motor circuit together with disconnections between the rostral supplementary motor area, rostral cingulate motor area, and cerebellum 2.
• Micrographia can also be observed as part of the clinical picture of additional neurodegenerative disorders, sometimes antedating the motor signs, or following focal basal ganglia lesions without any accompanying parkinsonism 3.
• The etiology of micrographia is doubtful, and levodopa only partially ameliorates letter stroke size, and only in some patients 3.
• Parkinsonian handwriting is often characterized by lack of fluency, slowness, and less frequently by micrographia, and deviations from kinematic laws of motion that govern normal movement may reflect impairments in motion planning, possible loss of automaticity, and reduced movement vigor 3, 4.

Key Factors Contributing to Micrographia

• Dysfunction of the basal ganglia circuitry induced by neurodegeneration or disruption by focal damage gives rise to micrographia 3.
• Bradykinesia and rigidity are not necessary for the development of micrographia, and micrographia in a patient with no signs of parkinsonism may prompt the clinician to perform imaging to exclude a focal basal ganglia lesion 3.
• Attention significantly improves both consistent and progressive micrographia, accompanied by recruitment of anterior putamen and dorsolateral prefrontal cortex 2.
• Levodopa improves consistent micrographia accompanied by increased activity and connectivity in the basal ganglia motor circuit, but has no effect on progressive micrographia 2, 5.