Cortical syndromes: aphasia, apraxia, agnosia, neglect, frontal signs
- Syndrome
The signs that show which lobe of the brain is damaged: problems with language, skilled movements, recognition, attention to one side or behavior.
See it in 3D: Frontal lobe · Parietal lobe · Temporal lobe · Occipital lobe · Insula · Corpus callosum · Motor cortex
What it is
Each lobe of the cerebral cortex has its own functions, so a lesion produces a recognizable cluster of signs. Aphasia (a language disorder), apraxia (loss of learned skilled movements without weakness), agnosia (failure to recognize despite intact senses) and neglect (ignoring one side of space) are tested at the bedside with simple tasks. Language usually sits in the left hemisphere, spatial attention in the right.
Key findings
- Language exam: fluency, comprehension, repetition, naming, reading and writing.
- Praxis: ask the patient to wave goodbye, show how to use a comb or a key, then imitate the examiner.
- Gnosis: name objects by sight, identify an object in the hand with the eyes closed (stereognosis) and recognize familiar faces.
- Neglect: line bisection, crossing out targets on a page, and extinction when both sides are touched at once.
- Frontal signs: disinhibition or apathy, perseveration, poor planning and a returning grasp reflex.
Pathophysiology
- Frontal lobe: the motor cortex, Broca area (left inferior frontal gyrus) for speech output, and the prefrontal cortex for planning, judgment and inhibition.
- Parietal lobe: the sensory cortex; on the dominant side, calculation, writing and finger and left–right recognition; on the nondominant side, attention to the opposite side of space and body.
- Temporal lobe: Wernicke area (left superior temporal gyrus) for comprehension, the hippocampus for new memories, and the upper part of the optic radiation.
- Occipital lobe: the primary visual cortex and visual association areas.
- Skilled movements are stored mainly in parietal and premotor networks linked through the corpus callosum.
Lesion site and the signs it produces
| Lobe | Dominant (usually left) | Nondominant (usually right) | Either side |
|---|---|---|---|
| Frontal | Broca (nonfluent) aphasia | Motor impersistence, flat or inappropriate affect | Contralateral weakness, disinhibition or apathy, perseveration, grasp reflex |
| Parietal | Gerstmann syndrome: agraphia, acalculia, finger agnosia, left–right confusion; ideomotor apraxia | Left neglect, denial of the deficit (anosognosia), dressing and constructional apraxia | Contralateral cortical sensory loss: astereognosis, agraphesthesia |
| Temporal | Wernicke (fluent) aphasia, verbal memory loss | Trouble recognizing music and tone of voice | Contralateral upper quadrant visual loss; memory loss if both sides are affected |
| Occipital | Alexia without agraphia (with a callosal lesion) | Visuospatial problems | Contralateral homonymous hemianopia; both sides: cortical blindness |
Common causes
- Stroke in the middle cerebral artery territory is the most common cause of sudden aphasia or neglect.
- Tumors (glioblastoma, metastases) cause cortical signs that progress over weeks.
- Alzheimer disease begins with memory loss and later adds aphasia, apraxia and agnosia.
- Frontotemporal dementia begins with changes in behavior or language with memory relatively spared.
- Head injury, encephalitis and abscesses are other causes.
Tests that confirm it
- CT or MRI of the brain locates the lesion; sudden onset needs urgent imaging as a possible stroke.
- Neuropsychological testing measures subtle deficits and follows their course.
Test yourself
Think of the answer, then tap the question to see it.
Which three tests separate Broca, Wernicke and conduction aphasia?
Fluency, comprehension and repetition: Broca is nonfluent with good comprehension, Wernicke is fluent with poor comprehension, conduction is fluent with good comprehension but poor repetition.
What is apraxia?
Inability to perform a learned skilled movement, such as using a comb, despite normal strength, coordination and understanding of the task.
Which lesion typically causes left neglect with denial of the deficit?
A lesion of the right (nondominant) parietal lobe, often a middle cerebral artery stroke.
What are the four elements of Gerstmann syndrome?
Agraphia, acalculia, finger agnosia and left–right confusion, from a dominant parietal lesion.
Connections
See it in 3D7
The structures of Durgical's 3D anatomy where it is found.
Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis.
Sources: Overview of Cerebral Function (MSD Manual Professional Edition, 2024); Aphasia (MSD Manual Professional Edition, 2024); Apraxia (MSD Manual Professional Edition, 2024); Agnosia (MSD Manual Professional Edition, 2024).
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Representative model, for educational purposes only.