Midbrain Flashcards
What are the two main parts of the midbrain?
- Tectum (superior and inferior colliculi). 2. Tegmentum (contains red nucleus, substantia nigra, and cranial nerve nuclei).
What is the function of the superior colliculus?
The superior colliculus is involved in visual reflexes and coordination of eye movements.
What is the function of the inferior colliculus?
The inferior colliculus is involved in auditory processing and reflex responses to sound.
What is the clinical significance of the substantia nigra?
Degeneration of the substantia nigra leads to Parkinson’s disease, characterized by tremors, rigidity, and bradykinesia.
What cranial nerves are associated with the midbrain?
CN III (oculomotor) and CN IV (trochlear).
What is Weber syndrome, and which structures are affected?
Weber syndrome is a midbrain stroke affecting the cerebral peduncle (corticospinal tract) and CN III, causing ipsilateral CN III palsy and contralateral hemiparesis.
What is the blood supply of the midbrain?
Supplied by the posterior cerebral artery (PCA) and superior cerebellar artery (SCA).
What is the function of the red nucleus?
The red nucleus is involved in motor coordination and is part of the extrapyramidal system.
What is the clinical significance of the periaqueductal gray (PAG)?
The PAG is involved in pain modulation and the fight-or-flight response.
What is the clinical significance of the tectum?
The tectum (superior and inferior colliculi) is involved in visual and auditory reflexes. Damage can affect eye movements and startle responses.
A patient presents with ipsilateral CN III palsy and contralateral hemiparesis. What is the most likely diagnosis?
Weber syndrome (midbrain stroke affecting the cerebral peduncle and CN III).
A patient with Parkinson’s disease has degeneration in which midbrain structure?
Substantia nigra.
What is the function of the medial longitudinal fasciculus (MLF) in the midbrain?
The MLF coordinates eye movements by connecting CN III, IV, and VI. Lesions cause internuclear ophthalmoplegia (INO).
What is the clinical significance of the oculomotor nerve (CN III) in the midbrain?
CN III controls most eye movements (except lateral rectus and superior oblique) and pupil constriction. Damage causes ptosis, diplopia, and a ‘down and out’ eye position.
What is the clinical significance of the trochlear nerve (CN IV) in the midbrain?
CN IV controls the superior oblique muscle, which intorts and depresses the eye. Damage causes vertical diplopia and difficulty reading or walking downstairs.
What is the role of the cerebral aqueduct in the midbrain?
The cerebral aqueduct connects the third and fourth ventricles and allows CSF flow. Obstruction can cause hydrocephalus.
A patient presents with vertical diplopia and difficulty walking downstairs. Which cranial nerve is likely affected?
CN IV (trochlear nerve).
A patient presents with ptosis, diplopia, and a ‘down and out’ eye position. Which cranial nerve is likely affected?
CN III (oculomotor nerve).
What is the clinical significance of the decussation of the superior cerebellar peduncle in the midbrain?
The superior cerebellar peduncle decussates in the midbrain, carrying efferent fibers from the cerebellum to the thalamus. Damage can cause ataxia.
What is the clinical significance of the interpeduncular fossa?
The interpeduncular fossa is a space between the cerebral peduncles where CN III emerges. It is also a site for CSF circulation.
A patient presents with a unilateral midbrain lesion affecting the red nucleus and cerebellothalamic fibers. What is the most likely clinical feature?
Contralateral tremor and ataxia (Benedikt syndrome).
Front
Back
Which structure in the midbrain is responsible for motor coordination and contains dopaminergic neurons? A) Red nucleus B) Superior colliculus C) Substantia nigra D) Inferior colliculus
C) Substantia nigra
Damage to the midbrain can result in which of the following clinical findings? A) Hemiballismus B) Weber’s syndrome C) Wallenberg’s syndrome D) Brown-Séquard syndrome
B) Weber’s syndrome
The superior colliculus in the midbrain is primarily involved in: A) Auditory processing B) Visual reflexes C) Pain modulation D) Sleep regulation
B) Visual reflexes
Which of the following is a function of the periaqueductal gray (PAG) in the midbrain? A) Regulation of heart rate B) Modulation of pain C) Control of eye movements D) Coordination of balance
B) Modulation of pain
The oculomotor nerve (CN III) originates from which part of the midbrain? A) Tectum B) Tegmentum C) Cerebral peduncles D) Basal ganglia
B) Tegmentum
Which midbrain structure is involved in the auditory pathway? A) Red nucleus B) Superior colliculus C) Inferior colliculus D) Substantia nigra
C) Inferior colliculus
Parinaud’s syndrome
characterized by vertical gaze palsy
The cerebral peduncles of the midbrain contain: A) Ascending sensory tracts B) Descending motor tracts C) Dopaminergic neurons D) Visual reflex fibers
B) Descending motor tracts
Which neurotransmitter is primarily associated with the substantia nigra in the midbrain? A) Serotonin B) Acetylcholine C) Dopamine D) GABA
C) Dopamine
The red nucleus in the midbrain is primarily involved in: A) Visual processing B) Motor coordination C) Auditory reflexes D) Pain modulation
B) Motor coordination
