Language is the most distinctive human cognitive function and the single most useful window into the dominant hemisphere. The bedside language exam takes about three minutes; it produces a level of localization that is hard to match with imaging alone in the acute setting. A patient who cannot name a watch but speaks fluently and follows simple commands has a different lesion from a patient who speaks in halting telegraphic phrases but understands every word. The two patients may be in adjacent rooms. The neurologist who can recognize the syndromes on hearing the first few sentences of conversation is several diagnostic steps ahead.

This page covers the language exam itself: the four components every aphasia exam needs to test, the syndromes the bedside findings define, and the disorders of speech production — dysarthria and apraxia of speech — that must be distinguished from language disorders before any aphasia classification is meaningful. The point throughout is the same: language is a network function, distributed across the dominant hemisphere, with each component vulnerable to lesions at specific cortical sites.

Language Is Not Speech

The first distinction at the bedside is between language and speech. Language is the cognitive function of converting thought into symbols and decoding symbols into thought. Speech is the motor act of producing the sounds. A patient with a brainstem stroke who cannot move their lips well has a speech disorder (dysarthria), but their language is intact: they can write, understand, name objects, and read normally. A patient with a stroke in the inferior frontal gyrus may speak the few words they produce clearly, but the words are wrong, sparse, agrammatic, or absent — a language disorder. Confusing the two is the most common error in the bedside cognitive exam.

The clinical test that distinguishes them is writing. Aphasic patients write the way they speak — with the same content errors, omissions, paraphasias, or agrammatism. Dysarthric patients write normally (assuming they can hold a pen). A patient whose oral speech is slurred but whose handwriting is grammatical and coherent has dysarthria. A patient whose speech is fluent but whose writing contains the same neologisms and word substitutions has aphasia.

The Four Components of the Aphasia Exam

Every aphasia exam needs to test four things, in a specific order. The order matters because each function depends in part on the ones tested before it.

1. Fluency

Fluency is the rate, prosody, length, and grammatical structure of spontaneous speech. It is assessed during the history, in the first thirty seconds of conversation. The decisions are made on two grounds:

• Effort and rate: normal conversation flows at about 100-150 words per minute, in phrases of five to ten words. Non-fluent speech is halting, effortful, slow (often well under 50 words per minute), and produced in short phrases of one to four words.
• Grammar: non-fluent speech is typically agrammatic (“telegraphic”) — content words are present (nouns, main verbs) but function words (articles, prepositions, conjunctions) and inflections are omitted. Fluent speech is grammatical even when its content is empty.

A useful prompt is to ask the patient to describe a picture (the standard “Cookie Theft” picture or any complex visual scene). A patient with non-fluent aphasia will produce a halting, effortful description with only the main nouns: “boy… cookie… falling… girl… water.” A patient with fluent aphasia will produce a rapid, grammatically intact but meaningless stream: “the thing is going over there and the other one with the things, you know, the things go on and on with the other ones.”

Fluency is the first major branch point of the aphasia tree. Non-fluent aphasia points to anterior dominant-hemisphere disease (Broca area, prefrontal, anterior insula). Fluent aphasia points to posterior dominant-hemisphere disease (Wernicke area, posterior temporal, parietal). Knowing only whether the patient is fluent puts you in the right half of the cortex.

2. Comprehension

Comprehension is tested at three levels of increasing difficulty:

• Single-step commands: “Close your eyes.” “Make a fist.” Use commands that do not require complex understanding or lateral spatial reasoning.
• Multi-step commands: “Touch your right ear with your left thumb, then point to the ceiling.” Multi-step commands integrate working memory and sequential processing.
• Syntactic comprehension: “Is a lion stronger than a tiger?” “The lion was killed by the tiger; who is dead?” These require parsing grammar to extract meaning. A patient may answer yes-no questions correctly but fail syntactically complex ones — a hallmark of mild Broca aphasia, which preserves comprehension at the simple level but breaks down on grammatical parsing.

Be careful about depending too heavily on commands that involve midline body movements (“close your eyes,” “stick out your tongue”), because these can be performed correctly through preserved subcortical (extrapyramidal) routes even in severe aphasia. Lateralized commands (“touch your left ear with your right hand”) are more discriminating.

3. Naming

Naming is the single most sensitive test in the language exam. Anomia is the most consistent finding in every aphasia. A patient may name the watch, the watchband, and the buckle correctly when shown them, but fail on the strap, the second hand, the winding stem. Confrontation naming — show the patient an object, ask “what is this?” — is the standard test. Use both common objects (watch, pen, glasses) and less common ones (winding stem, lapel, knuckle) to reveal mild anomia.

Patients with naming difficulties produce several recognizable types of errors:

• Word-finding pauses: the patient hesitates, circumlocutes, describes the function or appearance of the object (“the thing you tell time with”). This is the bedside presentation of mild anomia.
• Semantic paraphasias: substitutions of related words (calling a watch a “clock” or a “ring”). Common in transcortical sensory aphasia and Wernicke aphasia.
• Phonemic paraphasias: substitutions of sound (calling a watch a “watth,” “wash,” or “wath”). Common in conduction aphasia.
• Neologisms: invented words that are not real (“the gerflot is broken”). Suggest severe Wernicke or jargon aphasia.

The pattern of paraphasias often reveals the type of aphasia more reliably than the rate of speech.

4. Repetition

Repetition is the most localizing single test. The patient is asked to repeat phrases of increasing complexity: “ball,” “baseball,” “the cat is hungry,” “the brown puppy sleeps in the sunny yard,” and the classical “no ifs, ands, or buts.” Repetition depends on the arcuate fasciculus connecting Wernicke and Broca areas, and on the perisylvian language cortex generally. The clinical importance of repetition is that it dissociates from comprehension and production in characteristic ways:

• Repetition impaired with the rest of the aphasia indicates a perisylvian lesion — Broca, Wernicke, conduction, or global aphasia.
• Repetition preserved despite other language deficits indicates a transcortical aphasia — the perisylvian language circuit is intact but isolated from the rest of the dominant hemisphere.

This one distinction divides the aphasias into two large groups.

The Classical Aphasia Syndromes

The Boston classification organizes the aphasias by fluency, comprehension, and repetition. It is imperfect — real patients often have features of several syndromes, and “pure” forms are uncommon — but the framework structures the bedside exam efficiently.

Broca Aphasia

Halting, effortful, non-fluent speech with agrammatism and relatively preserved comprehension. Patients are typically aware of their language deficit and frustrated by it. Repetition is impaired. Naming is reduced. Reading aloud is laborious; reading comprehension is often better preserved than writing. The lesion is in the inferior frontal gyrus of the dominant hemisphere (Broca area, pars opercularis and triangularis), extending into the deep white matter and often the insula. A lesion confined to the cortical Broca area alone often produces only a transient deficit; persistent Broca aphasia usually reflects damage to the underlying white matter as well. A right hemiparesis is almost universal at presentation, because the motor strip and its descending fibers are next door.

Wernicke Aphasia

Fluent, often paraphasic speech with severely impaired comprehension. Patients speak in grammatically correct sentences that contain meaningless content — strings of correctly inflected words and neologisms, sometimes called “word salad.” Repetition is impaired. Naming is severely impaired. Reading and writing show the same deficits as speech. Crucially, patients are typically unaware of their deficit and may continue to speak normally to the examiner despite producing only nonsense — this is one of the most characteristic features of Wernicke aphasia and one that distinguishes it from psychiatric thought disorder. The lesion is in the posterior superior temporal gyrus of the dominant hemisphere. A right superior quadrantanopia is common (Meyer’s loop in the adjacent temporal lobe); a hemiparesis is typically absent.

Conduction Aphasia

Fluent speech with preserved comprehension but striking repetition impairment, often disproportionate to other deficits. Patients are typically aware of their errors and may correct themselves repeatedly when attempting to repeat (“the… the… the… brown… brown puppy… no, the brown puppy sleeps…”). Phonemic paraphasias are prominent. The classical lesion is in the arcuate fasciculus, the white matter tract connecting Wernicke and Broca areas, or in the overlying supramarginal gyrus. Conduction aphasia is uncommon as a pure presentation; small parietal strokes are the usual cause.

Global Aphasia

Non-fluent speech (often reduced to single words or stereotypes), severely impaired comprehension, impaired repetition, impaired naming, impaired reading and writing. A right hemiparesis is universal. The lesion is a large dominant-hemisphere infarct, most commonly from a proximal MCA occlusion, involving both Broca and Wernicke areas and the perisylvian cortex between them. Global aphasia carries a poor prognosis for full language recovery, though improvement to milder forms (typically Broca-type) is common over weeks to months.

The Transcortical Aphasias

The transcortical aphasias share preserved repetition with the rest of their deficits. They occur when the perisylvian language area (Broca, Wernicke, arcuate fasciculus) is intact but is isolated from the surrounding cortex by lesions of the watershed border zones — typically infarcts at the boundary between the MCA and ACA territories (anterior watershed) or between the MCA and PCA territories (posterior watershed).

• Transcortical motor aphasia: non-fluent, comprehension preserved, repetition preserved. The lesion is anterior to or above Broca area, often in the supplementary motor area or its connections. Patients produce minimal spontaneous speech but echo and repeat well.
• Transcortical sensory aphasia: fluent paraphasic speech, comprehension impaired, repetition preserved. The lesion is posterior to Wernicke area, in the temporo-parietal junction. The classical feature is echolalia — the patient repeats what the examiner says without understanding it.
• Mixed transcortical aphasia (isolation of the speech area): non-fluent, comprehension impaired, repetition preserved. The picture combines transcortical motor and transcortical sensory features and reflects bilateral watershed infarction isolating the perisylvian cortex on both fronts. The patient may produce no spontaneous speech but echo full sentences. The combination is most commonly seen after severe global hypoperfusion (cardiac arrest with watershed infarcts) or carbon monoxide poisoning.

Anomic Aphasia

Fluent speech with preserved comprehension and repetition but prominent word-finding difficulty. Patients are aware of their problem and circumlocute frequently. Anomic aphasia is the residual deficit after recovery from many of the other aphasia syndromes; it is also the typical aphasia of mild dominant-hemisphere injury and the most common aphasia in the chronic phase of recovery. The lesion can be in many sites, most commonly the angular gyrus, but anomia is so universal in language disturbance that the bedside finding of isolated anomia is not strongly localizing.

Subcortical Aphasia

Aphasia can result from deep lesions in the dominant hemisphere — typically the head of the caudate, the putamen, the internal capsule, or the thalamus. The patterns do not fit neatly into the Boston classification. Thalamic aphasia typically combines fluent speech with paraphasic content, fluctuating comprehension that may improve with attention, and preserved repetition. Striatocapsular aphasia can present with reduced speech output, paraphasic errors, and variable comprehension. The recognition of subcortical aphasia is mostly important because it argues for vascular disease in a small-vessel distribution and because the patient’s deficit often fluctuates more than cortical aphasias do.

Disorders of Reading and Writing

Alexia

Acquired inability to read can occur with or without an aphasia. Pure alexia (alexia without agraphia) is the syndrome of inability to read while writing is preserved — the patient can write a sentence and then be unable to read it back, sometimes within seconds. The classical lesion is the left occipital lobe combined with the splenium of the corpus callosum — visual information reaches the right occipital cortex but cannot cross to the left language areas. The patient often has a right hemianopia accompanying the alexia, and color anomia is sometimes present. This is one of the more elegant syndromes in clinical neurology and one of the easiest to miss without specifically asking the patient to read.

Alexia with agraphia — inability to read or write with relatively preserved spoken language — is the syndrome of dominant angular gyrus lesions. It is part of Gerstmann syndrome (dominant angular gyrus) when it accompanies acalculia, right-left disorientation, and finger agnosia.

Agraphia

Writing is the language modality that fails earliest and recovers last in most aphasias. Pure agraphia is uncommon; agraphia accompanying other language deficits is the rule. The pattern of writing errors mirrors the pattern of speech errors: agrammatic agraphia in Broca, paraphasic agraphia in Wernicke, phonemic agraphia in conduction. The most useful clinical contribution of writing is in confirming or excluding aphasia in patients with dysarthria (see opening section).

Disorders of Speech Production: Dysarthria and Apraxia of Speech

Before classifying a patient’s communication problem as aphasia, exclude these two motor speech disorders.

Dysarthria

Dysarthria is impairment of the motor production of speech. The patient produces the words they intend but cannot articulate them clearly. Several patterns localize:

• Spastic dysarthria: slow, strained, “strangled” speech with consonant imprecision and reduced pitch range. Bilateral corticobulbar lesions — pseudobulbar palsy from multiple strokes, ALS, advanced MS.
• Flaccid dysarthria: breathy, nasal, with reduced loudness and rapid fatigue. Lower motor neuron lesions of bulbar muscles — bulbar ALS, myasthenia gravis, brainstem stroke involving CN IX, X, XII.
• Ataxic dysarthria: irregular rate and rhythm, “scanning” speech with prolonged or irregularly emphasized syllables. Cerebellar disease — degenerative ataxia, MS plaque in the cerebellum.
• Hypokinetic dysarthria: monotone, hypophonic, festinating, with rapid blurred speech. Parkinson disease and other hypokinetic syndromes.
• Hyperkinetic dysarthria: variable, often jerky speech disrupted by involuntary movements. Chorea, dystonia, tics.
• Mixed dysarthria: ALS commonly produces a combination of spastic and flaccid dysarthria; multiple system atrophy combines ataxic, hypokinetic, and spastic features.

Apraxia of Speech

Apraxia of speech is a disorder of speech motor programming — the patient knows what they want to say and how to say it, but cannot consistently generate the correct motor commands. Speech is effortful, with inconsistent articulatory errors, groping for sounds, and longer words that fall apart. Repetition often makes the patient worse rather than better. The cardinal feature is variability: the same word may come out differently each time the patient attempts it. The lesion is typically in the left inferior frontal cortex and underlying white matter, often overlapping with Broca aphasia. Apraxia of speech can occur in isolation (pure motor speech disorder) but more commonly accompanies Broca aphasia.

Right Hemisphere Communication Disorders

Non-dominant hemisphere lesions do not produce classical aphasia, but they impair communication in their own characteristic ways. Patients can be fluent, comprehend literal speech, repeat, name, read, and write, yet they communicate poorly:

• Aprosodia: flat, monotone speech without emotional inflection (motor aprosodia from anterior right-hemisphere lesions) or difficulty interpreting the emotional tone of others’ speech (sensory aprosodia from posterior right-hemisphere lesions). The patient who speaks like a robot or who cannot tell whether the examiner is asking a question or making a statement has aprosodia.
• Loss of figurative language: difficulty understanding metaphor, sarcasm, idioms, and indirect speech. The patient takes everything literally and may laugh or react inappropriately to non-literal cues.
• Disorganized discourse: tangential, off-topic narrative; difficulty pulling out the main point of a story; impaired pragmatic use of language.

Primary Progressive Aphasia

Aphasia is occasionally the presenting feature of neurodegenerative disease. The three recognized variants of primary progressive aphasia have distinct profiles:

• Non-fluent/agrammatic variant: effortful, agrammatic speech with apraxia of speech and preserved single-word comprehension. Often accompanied by progressive supranuclear palsy or corticobasal degeneration features over time. The pathology is most often a tauopathy.
• Semantic variant (semantic dementia): fluent speech with progressive loss of word and object meaning, from anterior temporal degeneration. Patients ask “what is a hamburger?” and can no longer recognize common objects. Repetition is preserved; single-word comprehension is severely impaired. The pathology is TDP-43.
• Logopenic variant: word-finding pauses with relatively preserved single-word comprehension but impaired repetition of phrases. The pathology is usually Alzheimer disease.

The classification matters because the underlying pathology — and the family of disorders — differs by variant, with implications for prognosis and counseling.

🔍 Did You Know?

About 90-95% of right-handers have left-hemisphere dominance for language. Among left-handers, language dominance is more variable: about 70% are still left-dominant, 15% are right-dominant, and 15% show bilateral language representation. A left-handed patient with a left-hemisphere stroke who develops aphasia tends to recover more completely than a right-handed patient with a similar lesion, presumably because of more distributed bilateral representation. A right-handed patient with aphasia from a right-hemisphere stroke (“crossed aphasia”) is rare and important to recognize, because the localization rules from the left hemisphere generally apply in reverse.

Pitfalls and Pearls

• Always test writing. Distinguishing aphasia from dysarthria takes less than thirty seconds of asking the patient to write a sentence and is the single most discriminating bedside test.
• Fluency divides anterior from posterior. Non-fluent = anterior. Fluent = posterior. This single distinction is the most useful in the aphasia exam.
• Repetition divides perisylvian from extra-perisylvian. Preserved repetition with deficits elsewhere = transcortical. Impaired repetition = Broca, Wernicke, conduction, or global.
• Patients with Wernicke aphasia are typically unaware. The combination of fluent paraphasic speech with apparent indifference to the deficit is highly characteristic and often distinguishes Wernicke aphasia from psychiatric disorder.
• Patients with Broca aphasia are typically aware. They are frustrated, often depressed, and may avoid speaking. Their cognition is otherwise intact.
• Repetition out of proportion to other deficits is conduction aphasia. Watch for phonemic paraphasias and self-correction attempts.
• Echolalia is transcortical aphasia until proven otherwise. A patient who repeats everything you say but cannot follow commands has the syndrome of isolation of the speech area or transcortical sensory aphasia.
• “Pure alexia” exists. A patient who can write but cannot read what they have written has a left occipital lesion with splenial involvement until proven otherwise.
• Aprosodia is the right-hemisphere equivalent of aphasia. Patients with right-hemisphere lesions sound flat or fail to read emotional tone, and their communication suffers even though their words are correct.
• Progressive language deficits in a previously well person are primary progressive aphasia until proven otherwise. Time course (months to years) distinguishes it from stroke; family history and other neurologic features help separate the variants.

References

1. Campbell WW. DeJong’s The Neurologic Examination. 7th ed. Philadelphia: Lippincott Williams & Wilkins; 2013. Chapter 9.
2. Goodglass H, Kaplan E. The Assessment of Aphasia and Related Disorders. 3rd ed. Philadelphia: Lippincott Williams & Wilkins; 2000.
3. Damasio AR. Aphasia. N Engl J Med. 1992;326(8):531-539.
4. Gorno-Tempini ML, Hillis AE, Weintraub S, et al. Classification of primary progressive aphasia and its variants. Neurology. 2011;76(11):1006-1014.
5. Hillis AE. Aphasia: progress in the last quarter of a century. Neurology. 2007;69(2):200-213.
6. Duffy JR. Motor Speech Disorders: Substrates, Differential Diagnosis, and Management. 4th ed. Elsevier; 2020.
7. Mesulam MM. Principles of Behavioral and Cognitive Neurology. 2nd ed. Oxford University Press; 2000.

Brain illustration: “Brain Surface Gyri” by James.mcd.nz, CC BY-SA 4.0, via Wikimedia Commons; region labels and connections added by Neuro.Wiki.