Clinical presentation of motor aphasia (Broca's area)
Acute onset of motor aphasia is often accompanied by associated neurological deficit. Characteristic features include:
- Speech disorders: the patient practically stops speaking, responses become single-worded ("telegraphic style"). Marked difficulties arise with word-finding, object naming, and gross impairments of sentence grammatical structure (agrammatism).
- Motor sphere: typically accompanied by mild right-sided hemiparesis (e.g., with predominant weakness in the right upper extremity and a tendency for it to drop during the outstretched arms test), accompanied by hyperreflexia on the right side.
Such symptoms may develop suddenly, for example, in dissection of the left internal carotid artery (ICA), triggered by a sharp neck movement.
Neuroimaging in Broca's area infarction
Magnetic resonance imaging (MRI) in various modes is used to confirm the diagnosis and specify the localization of the ischemia focus:
- Diffusion-weighted imaging (DWI): the infarct zone in the middle cerebral artery territory (predominantly in the inferior frontal gyrus, Brodmann area 44) appears hyperintense (brighter than healthy tissue). A focus in the precentral gyrus, supplied by the precentral sulcal artery, may also be visualized.
- T2-weighted imaging and FLAIR mode: the lesion in Broca's area and the precentral gyrus also appears as areas of hyperintense signal.
- MR angiography: reveals a significant decrease in blood flow in the left ICA.
- Neck MRI (T1 and T2 at the C2 level): reveals a hematoma in the internal carotid artery wall, which is a direct sign of its dissection.
Clinical presentation of sensory aphasia (Wernicke's area)
Lesions of the left parietal lobe involving Wernicke's area lead to a completely different clinical picture:
- Speech functions: severe jargonaphasia develops. The patient does not understand spoken speech, giving meaningless and lengthy answers to simple questions. Object naming is impaired (use of neologisms) and reading is impaired (even of their own written text).
- Preserved functions: nevertheless, patients can understand instructions given via gestures and retain writing, counting, and copying skills (both drawings and text).
- Motor sphere: mild right-sided hemiparesis may also be observed.
A frequent cause of such a lesion is cardiogenic embolism secondary to prolonged cardiac arrhythmia (thrombotic mass formation in the left atrium).
Treatment principles and outcomes
In the acute period of ischemic stroke caused by dissection or cardiogenic embolism, the mainstay of pharmacotherapy is the use of anticoagulants (heparin transitioning to warfarin) to prevent microembolism.
The recovery process depends on the cause:
- In ICA dissection, the thrombus in the wall resolves, the endothelial defect heals, and normal blood flow typically restores within 4–6 months. With rehabilitation (speech therapy, exercise therapy), complete regression of the neurological deficit is possible.
- In Wernicke's area lesions, despite intensive speech therapy, residual deficits in the form of semantic paraphasia and incomplete speech comprehension may persist in the outcome.
Briefly: answers to topical questions
What anatomical parts does the internal capsule consist of?
The internal capsule consists of the anterior limb, genu, posterior limb, and retrolentiform part.
- Anterior limb (crus anterius capsulae internae) contains frontothalamic and frontopontine tracts.
- Genu is the site of passage of the corticonuclear tract.
- Posterior limb includes anterior and posterior parts.
- Retrolentiform part (pars retrolentiformis) is located posterior to the lentiform nucleus.
Which subcortical nuclei form the boundaries of the internal capsule?
The internal capsule is topographically bounded by the thalamus medially and the lentiform nucleus laterally.
- Thalamus (thalamus) is located medial to the internal capsule; it is separated from the capsule by the external medullary lamina.
- Lentiform nucleus (nucleus lentiformis) is located lateral to the internal capsule and includes the globus pallidus and putamen.
- Caudate nucleus (nucleus caudatus) is located in close proximity to the internal capsule; sources do not specify that its head and tail directly border the capsule.
Which pathway tracts pass through the anterior limb of the internal capsule?
Descending and ascending pathways connecting the frontal lobe with the thalamus and pons pass through the anterior limb of the internal capsule.
- Frontothalamic tract connects the frontal lobe cortex with thalamic nuclei.
- Frontopontine tract runs from the frontal cortex to the pontine nuclei.
Which pathway passes through the genu of the internal capsule?
The descending motor corticonuclear tract passes through the genu of the internal capsule.
- Corticonuclear tract (tractus corticonuclearis) carries motor fibers to the face. It runs from the cerebral cortex to the motor cranial nerve nuclei, providing voluntary movements of facial muscles. Fibers of this tract have a strict somatotopic organization.
Which motor pathways pass through the anterior two-thirds of the posterior limb of the internal capsule?
The corticospinal tract passes through the anterior two-thirds of the posterior limb of the internal capsule.
- Corticospinal tract (tractus corticospinalis) is a part of the pyramidal tract carrying motor fibers. The fibers have a strict somatotopic organization: from anterior to posterior, fibers run to the arm, then the trunk, then the leg.
Which sensory pathways pass through the posterior third of the posterior limb of the internal capsule?
Somatosensory, visual, and auditory pathways pass through the posterior part of the posterior limb of the internal capsule.
- Somatosensory pathways conduct sensitivity to the cerebral cortex.
- Visual pathways comprise the optic radiation.
- Auditory pathways comprise the acoustic radiation (radiatio acustica).
- Temporopontine fibers connect the temporal lobe with the pons.
Which pathways pass through the retrolentiform part of the internal capsule?
The following pass through the retrolentiform part of the internal capsule:
- Posterior thalamic radiations (radiationes thalamicae posteriores).
- Parieto-occipitopontine fasciculus (fasciculus parietooccipitopontinus).
What classic clinical syndrome develops with a complete unilateral lesion of the internal capsule?
A complete unilateral lesion of the internal capsule results in a syndrome including motor and sensory disturbances on the contralateral side of the body.
- Contralateral hemiplegia or severe hemiparesis occurs due to damage to the corticospinal tract fibers in the posterior limb of the internal capsule.
- Hemiperesthesia or hemianesthesia represents a cerebral pathway-type sensory disorder.
- Central facial palsy — paralysis of the lower facial muscles on the contralateral side when the corticonuclear pathway is involved.
Class and exam questions
What is the difference between speech in Broca's and Wernicke's aphasia?
In Broca's aphasia, speech is sparse, "telegraphic", with agrammatism and preserved comprehension. In Wernicke's aphasia, speech is fluent but meaningless (jargonaphasia), and the comprehension of both spoken and one's own speech is severely impaired.
What is arterial dissection?
This is a tear in the vessel wall with hematoma formation within it, leading to narrowing of the arterial lumen and the risk of thrombosis followed by embolism.
Which MRI sequence best visualizes an acute ischemic stroke?
The most sensitive imaging mode in the hyperacute stage is diffusion-weighted imaging (DWI), where the infarct zone appears bright white (hyperintense).
What else to study on this topic
- Pathogenesis of cardiogenic embolism
- MR angiography technique
- MRI sequences: T1, T2, FLAIR, and DWI
- Blood supply anatomy of the cerebral cortex (MCA territory)
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