Neuroanatomy
Brain, brainstem, cranial nerves, spinal tracts, ventricles, and cerebral vasculature.
32 entriesCerebrum: 7Brainstem & cerebellum: 4Cranial nerves: 12Spinal tracts: 3Ventricles & CSF: 2Cerebral vasculature: 4
Nerves (15)
- Abducens nerve (CN VI) HYSupplies the lateral rectus. Its long course along the clivus and through the cavernous sinus makes it the cranial nerve most often affected by raised intracranial pressure, causing horizontal diplopia.
- Accessory nerve (CN XI) HYMotor nerve to sternocleidomastoid and trapezius, arising from the upper cervical cord. It crosses the posterior triangle superficially, where lymph node biopsy can injure it and cause shoulder droop.
- Corticospinal tract HYMain voluntary motor pathway from the motor cortex to the spinal cord. It crosses in the lower medulla; damage causes upper motor neuron signs — weakness, spasticity, hyperreflexia and an extensor plantar response.
- Dorsal column–medial lemniscus pathway HYAscending pathway for fine touch, vibration and proprioception. It runs up the same side of the spinal cord and crosses in the medulla, so cord lesions cause ipsilateral loss and a positive Romberg sign.
- Facial nerve (CN VII) HYMotor to the muscles of facial expression, with taste from the anterior tongue and parasympathetic supply to the lacrimal and submandibular/sublingual glands. Whether the forehead is spared separates a central (stroke) from a peripheral (Bell) palsy.
- Glossopharyngeal nerve (CN IX) Mainly sensory — posterior tongue, oropharynx and middle ear, plus the carotid sinus and body. It is the afferent limb of the gag reflex and supplies the parotid gland (parasympathetic) and stylopharyngeus.
- Hypoglossal nerve (CN XII) HYMotor nerve to the tongue. A lower motor neuron lesion makes the protruded tongue deviate toward the weak side, with atrophy and fasciculations.
- Oculomotor nerve (CN III) HYSupplies four extraocular muscles, levator palpebrae and the pupillary constrictor. A palsy gives a "down and out" eye with ptosis; a blown pupil signals compression (aneurysm or herniation) rather than diabetic ischemia.
- Olfactory nerve (CN I) Special sensory nerve for smell. Its fibers pass through the cribriform plate to the olfactory bulb, so head trauma and anterior fossa tumors cause anosmia.
- Optic nerve and visual pathway (CN II) HYCarries vision from the retina to the occipital cortex through the chiasm, tracts and radiations. The pattern of a visual field defect localizes the lesion, and CN II is the afferent limb of the pupillary light reflex.
- Spinothalamic tract HYAscending pathway for pain, temperature and crude touch. Its fibers cross within one or two segments of entering the cord, so cord lesions cause contralateral loss; syringomyelia damages the crossing fibers.
- Trigeminal nerve (CN V) HYLargest cranial nerve — sensation from the face, scalp, eye, nose and mouth in three divisions, plus motor supply to the muscles of mastication. Trigeminal neuralgia and shingles of V1 are the classic problems.
- Trochlear nerve (CN IV) HYThinnest cranial nerve and the only one to exit the back of the brainstem. It supplies the superior oblique; a palsy causes vertical diplopia worse on looking down and a compensatory head tilt away from the affected side.
- Vagus nerve (CN X) HYLongest cranial nerve — motor to the palate, pharynx and larynx, and parasympathetic supply to the thoracic and abdominal viscera down to the distal transverse colon. A lesion causes hoarseness, dysphagia and a uvula deviated away from the lesion.
- Vestibulocochlear nerve (CN VIII) HYSpecial sensory nerve for hearing (cochlear part) and balance (vestibular part). It runs with CN VII through the internal acoustic meatus, where a vestibular schwannoma causes unilateral hearing loss.
Arteries (3)
- Cerebral arteries (ACA, MCA, PCA) HYThe three paired arteries that supply the cerebral hemispheres. Each territory gives a recognizable stroke syndrome; the MCA is the most commonly affected.
- Circle of Willis HYArterial ring at the base of the brain joining the carotid (anterior) and vertebrobasilar (posterior) circulations. It provides collateral flow, and its branch points are where berry aneurysms form.
- Vertebrobasilar system HYThe posterior circulation — the vertebral arteries join to form the basilar artery, which supplies the brainstem, cerebellum and (through the PCAs) the occipital lobes. Its strokes cause vertigo, crossed signs and, with basilar occlusion, coma or locked-in syndrome.
Veins (1)
Organs (11)
- Basal ganglia HYDeep gray-matter nuclei that modulate movement through direct and indirect pathways. Their disorders cause either too little movement (Parkinson disease) or too much (Huntington chorea, hemiballismus).
- Cerebellum HYCoordinates movement, balance and eye movements. Hemisphere lesions cause ipsilateral limb ataxia, vermis lesions cause truncal and gait ataxia, and cerebellar strokes can swell and compress the brainstem.
- Cerebral cortex and lobes HYThe folded gray matter of the cerebral hemispheres, organized into frontal, parietal, temporal and occipital lobes with specialized areas for movement, sensation, language and vision. Lesion location predicts the deficit.
- Hypothalamus HYSmall part of the diencephalon that controls the pituitary, autonomic nervous system, temperature, hunger, thirst and circadian rhythm. Its disorders include central diabetes insipidus and craniopharyngioma.
- Internal capsule HYCompact band of white matter carrying motor and sensory fibers between the cortex and the brainstem. A small (lacunar) infarct here can cause a pure motor hemiparesis of the face, arm and leg.
- Limbic system HYNetwork of medial temporal and diencephalic structures for memory, emotion and behavior. The hippocampus and mammillary bodies are damaged in Alzheimer disease, Wernicke–Korsakoff syndrome and HSV encephalitis.
- Medulla oblongata HYLowest part of the brainstem, continuous with the spinal cord at the foramen magnum. It contains the cardiorespiratory centers, the nuclei of CN IX–XII and the pyramidal decussation; PICA strokes cause the lateral medullary (Wallenberg) syndrome.
- Midbrain HYUppermost part of the brainstem, around the cerebral aqueduct. It contains the CN III and IV nuclei, the substantia nigra and the corticospinal tracts in the cerebral peduncles, and is compressed in transtentorial herniation.
- Pituitary gland HYMaster endocrine gland in the sella turcica below the optic chiasm, with anterior (hormone-producing) and posterior (ADH, oxytocin) lobes. Adenomas cause hormone excess, hypopituitarism and bitemporal hemianopia.
- Pons HYMiddle part of the brainstem that links the cerebrum to the cerebellum. It holds the nuclei of CN V–VIII and horizontal gaze centers; basilar artery occlusion causes locked-in syndrome.
- Thalamus HYPaired relay station of the diencephalon. Almost all sensory information (except smell) and motor loops pass through it to the cortex; thalamic strokes cause contralateral sensory loss and sometimes severe pain.
Spaces & regions (2)
- Cranial meninges and intracranial hemorrhage HYThree membranes — dura, arachnoid and pia — that cover the brain and define the epidural, subdural and subarachnoid spaces. Each space has its own classic bleed and CT appearance.
- Ventricular system and CSF HYFour interconnected cavities in the brain that produce and circulate cerebrospinal fluid. Blockage or impaired absorption causes hydrocephalus, including normal pressure hydrocephalus in older adults.