General Symptomatology of Lesions
Parietal cortex damage is accompanied by a complex of disorders based on impairment of working memory mechanisms. Due to this failure, the brain loses the ability to retain and actively use the information required for current activities.
Key clinical manifestations include:
- Amnestic aphasia. The patient begins to forget individual words. In the vast majority of cases, nouns are specifically lost from the active lexicon.
- Circumlocution (substitution symptom). The inability to recall the necessary word is compensated by verbosity. The patient describes the object through its function (for example, instead of saying "pen", they say "that which we usually use to write on paper").
- Acalculia. A pronounced arithmetic disorder occurs—the patient loses the ability to perform mathematical operations.
Angular Gyrus Syndrome (*Gyrus angularis*)
Isolated damage to the angular gyrus is of particular interest. The main condition for the development of the specific clinical picture in this pathology is the strict absence of concomitant damage to the classic speech centers (Wernicke's area and Broca's area).
With such a localized defect, the diagnosis is anomic aphasia.
The pathogenesis of this condition lies in the disconnection of brain centers. There is a physical disruption of the transmission of visual information to Wernicke's sensory speech area. The eyes see the object or text, but the brain cannot correlate the visual image with its verbal equivalent.
Clinical Picture of Anomic Aphasia
Because the classic speech centers are unaffected, the patient shows a clear dissociation between preserved and impaired functions.
What is completely preserved:
- Perception of all auditory information.
- Understanding of others' spoken speech.
- Ability to repeat heard phrases.
What is grossly impaired:
- Understanding of any written speech (the patient sees letters but does not comprehend the meaning of what is read).
- Comprehension of drawn pictures and images.
- Naming demonstrated objects (anomia).
Thus, when examining such a patient, we observe that they easily perceive speech by ear and can repeat phrases, yet they fail tests on reading, image analysis, and direct object naming.