Brainstem structures | Functions | Centers | Symptoms |
---|---|---|---|
Midbrain (rostral to the pons and caudal to the thalamus and the basal ganglia) | Eye movements | Cranial nerve nuclei: III oculomotor nerve (mainly motor) IV trochlear nerve (motor) | Oculomotor signs: Ptosis (III) Ophthalmoplegia (III, IV) |
Pupillary size: sphincter pupillae and muscles of the ciliary body, pupil light reflex | Cranial nerve nuclei: III oculomotor nerve | Pupillary anomalies: Myosis (sympathetic lesion) Mydriasis (parasympathetic lesion) Anisocoria | |
Movement control | Substantia nigra | Parkinsonian syndrome and movement disorders (hemichorea, hemiballism, dystonia, tremor, asterixis, pseudo-athetosis, non-epileptic myoclonus) | |
Posture tone | Red nucleus | Postural tone impairment | |
Posture/auditory and visual integration | Accessory optic tractus | Balance disorder | |
Posture and movement integration | Tectum (dorsal part) | Balance disorder | |
Posture and inhibitor motor centers | Tegmentum (ventral portion) (basal ganglia and thalamus connections) | Involuntary movements | |
Sleep/wake cycles, alertness, and arousal | ARAS: composed of almost 100 nuclei, including locus coeruleus-raphe nuclei with neocortex connections | Sleep disturbance Consciousness disorders | |
Central thermic regulation | ARAS-hypothalamus connections | Hypo/hyperthermia | |
Pons (between the medulla and the midbrain) | Facial sensitivity, muscles of mastication | Cranial nerve nuclei: V trigeminal nerve (sensory and motor) | Facial symptoms: Facial dysesthesia Oculomotor signs: Corneal/ciliary reflex impairment |
Facial muscles and taste from the anterior 2/3 of the tongue (VII) | Cranial nerve nuclei: VII facial nerve (sensory and motor) | Facial symptoms: Peripheral facial palsy | |
Eye movement (abduction) | Cranial nerve nuclei: VI abducens nerve (motor) | Oculomotor signs: Ophthalmoplegia | |
Posture, sensation of rotation, gravity, and sound | Cranial nerve nuclei: VIII vestibulocochlear nerve (mostly sensory) Cerebellum tract | Altered audition (VIII) Balance disorders (VIII and cerebellum tract) | |
Posture Posture and inhibitor motor center | Spinocerebellar tracts Tegmentum (thalamus and basal nuclei connections) | Cerebellar ataxia Involuntary movement | |
Motor efference integration Sensory efference integration | Tracts carrying signals to the thalamus | Motor deficit Sensory deficit | |
Consciousness, alertness, and sleep regulation | Tracts carrying signals to the thalamus | Sleep disturbance Consciousness disorders | |
Sleep/wake cycles, alertness, and arousal | ARAS: composed of almost 100 nuclei, including raphe nuclei and locus coeruleus-raphe nuclei-neocortex connections | Sleep disturbance Consciousness disorders | |
Emotion | ARAS: locus coeruleus and amygdala connections | Anxiety and post-traumatic stress disorder (PTSD) | |
Central thermic regulation | ARAS-hypothalamus connections | Hypo/hyperthermia | |
Respiratory drive: respiratory rate and tidal volume control | Pedunculopontine tegmentum, locus coeruleus, lateral parabrachial respiratory group, and Kölliker-Fuse nuclei | Respiratory drive dysfunction: Kölliker-Fuse and parabrachial nuclear: increase tidal volume, decrease respiratory rate Lower part/ponto-peduncular injury: respiratory asynchronism | |
Medulla (lower half of the brainstem, connects the higher levels of the brain to the spinal cord) | Taste from the posterior 1/3 of the tongue | Cranial nerve nuclei: IX glossopharyngeal (sensory and motor) | Tongue sensory impairment |
Pharyngo-laryngeal reflex | Cranial nerve nuclei: IX glossopharyngeal nerve X vagus nerve (sensory and motor) XI spinal nerve (motor) | Oro-pharyngo-laryngeal anomalies: Dysphagia (swallowing impairment) Dysphonia Velo-pharyngo-laryngeal impairment Absence of pharyngeal/gag reflex | |
Glossal muscles | XII hypoglossal (mainly motor) | Tongue motor impairment (fasciculation, motor deficit) | |
Cough | IX glossopharyngeal nerve X vagus nerve | Absence of cough reflex (IX, X) | |
Posture | Spinocerebellar tracts | Cerebellar ataxia | |
Regulation of autonomic nervous system: | Sympathetic nuclei Parasympathetic nuclei: vagus nerve (X) control of the heart, lung, digestive tracts | Autonomic dysfunction | |
Cardiac regulation | Sympathetic nuclei Parasympathetic nuclei: vagus nerve (X) control of the heart, lung, digestive tracts | Oculocardiac reflex impairment (X) Dysautonomia: tachycardia (parasympathetic impairment), bradycardia (sympathetic impairment), sudden death | |
Vasomotor regulation | Hemodynamic failure: Dysautonomia with hypertension (parasympathetic impairment), hypotension (sympathetic impairment) | ||
Gastrointestinal motility | Gastrointestinal motility anomalies | ||
Respiratory drive: respiratory rate and tidal volume control | Respiratory centers: dorsal respiratory complex | Respiratory drive dysfunction: respiratory rate irregularities and ataxic breathing, hyperventilation, respiratory-ventilator asynchronism, central apnea | |
Microbiota gut-brain axis, senses and peripheral inflammation modulation | Vagus nerve (X) | Maladaptive immune response, gut-brain axis impairment | |
Tracts all along the brainstem | Connection of the oculomotor nerves (see Fig. 1) | Medial longitudinal fasciculus | Internuclear ophthalmoplegia |
Motor information from the periphery to supratentorial structures | Corticospinal tract Pyramidal and extrapyramidal tracts | Motor deficit, locked-in syndrome Tetrapyramidal and extrapyramidal syndromes with movement disorders (tremor) Non-epileptic myoclonus | |
Sensory information from the periphery to supratentorial structures | Posterior column-medial lemniscus pathway and spinothalamic tracts | Sensory deficit | |
Oculosympathetic control | Centers control of the ciliary nerve, superior tarsal muscle, pupillary sphincter/dilator | Horner’s syndrome (ptosis, myosis, enophtalamos, anhidrosis) |