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Neurologic
62 entries across 8 regions · 298 questions
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Back
- Cauda equinaHY NerveBundle of lumbar and sacral nerve roots descending in the lumbar cistern below the end of the spinal cord. Compression causes cauda equina syndrome, a surgical emergency.
- Greater occipital nerve NerveMedial branch of the dorsal ramus of C2 that supplies the skin of the back of the scalp. Its irritation causes occipital neuralgia, which responds to nerve block.
- Intervertebral discHY JointFibrocartilaginous joint between vertebral bodies, made of a tough anulus fibrosus around a gel-like nucleus pulposus. Lumbar disc herniation at L4–L5 or L5–S1 causes sciatica.
- Spinal cordHY OrganContinuation of the medulla within the vertebral canal, ending at the conus medullaris at about L1–L2 in adults. Its blood supply and level of termination explain spinal cord injury syndromes and safe lumbar puncture sites.
- Spinal meninges and spacesHY Space / regionThree membranes (dura, arachnoid, pia) and the spaces between them surrounding the spinal cord. The epidural space is the target of epidural anesthesia, and the lumbar cistern is sampled by lumbar puncture.
- Spinal nerves and rootsHY NerveThe 31 pairs of mixed nerves formed from dorsal (sensory) and ventral (motor) roots. Knowing where each root exits and what it supplies lets you localize radiculopathy.
- Vertebral arteryHY ArteryFirst branch of the subclavian artery, ascending through the cervical transverse foramina to join its partner and form the basilar artery. Dissection and subclavian steal are the key clinical problems.
Thorax
Abdomen
Pelvis & Perineum
- Pelvic autonomic nervesHY NerveSympathetic hypogastric nerves and parasympathetic pelvic splanchnic nerves (S2–S4) that meet in the inferior hypogastric plexus to control the bladder, rectum and sexual function. They are at risk in prostate and rectal surgery.
- Pudendal nerveHY NerveMain somatic nerve of the perineum (S2–S4), supplying the external anal and urethral sphincters, the perineal muscles and perineal skin. It is blocked at the ischial spine in labor and can be stretched in childbirth or entrapped in cyclists.
- Sacral plexusHY NerveNerve network on the posterior pelvic wall (L4–S4) that gives the sciatic, gluteal and pudendal nerves. It supplies the buttock, posterior thigh, nearly all of the leg and foot, the pelvic floor and the perineum.
Upper Limb
- Axillary nerveHY NerveBranch of the posterior cord that passes through the quadrangular space around the surgical neck of the humerus to supply deltoid and teres minor.
- Brachial plexusHY NerveNetwork formed by the ventral rami of C5–T1 that supplies the motor and most of the sensory innervation of the upper limb.
- Carpal tunnelHY Space / regionOsseofibrous tunnel on the palmar wrist, formed by the carpal bones and the flexor retinaculum, that carries the median nerve and nine long flexor tendons.
- Long thoracic nerveHY NerveBranch arising directly from the C5–C7 roots that supplies serratus anterior; injury causes medial winging of the scapula.
- Median nerveHY NerveFormed by roots from the lateral and medial cords. It supplies most of the anterior forearm and the thenar muscles, and passes through the carpal tunnel.
- Musculocutaneous nerve NerveLateral cord branch that pierces coracobrachialis, supplies the anterior arm muscles, and ends as the lateral cutaneous nerve of the forearm.
- Radial nerveHY NerveLargest branch of the brachial plexus (posterior cord). It supplies all extensor muscles of the arm and forearm and winds around the humerus in the radial groove.
- Ulnar nerveHY NerveMedial cord branch that passes behind the medial epicondyle and through Guyon's canal. It supplies most intrinsic hand muscles and the medial 1½ digits.
Lower Limb
- Common fibular nerveHY NerveLateral terminal branch of the sciatic nerve that winds around the fibular neck — the most commonly injured nerve of the lower limb. Injury causes foot drop and numbness of the dorsum of the foot.
- Femoral nerveHY NerveLargest branch of the lumbar plexus (L2–L4), supplying the hip flexors and knee extensors and the skin of the anterior thigh and medial leg. Lesions cause knee buckling and a lost patellar reflex.
- Obturator nerve NerveLumbar plexus branch (L2–L4) that runs along the lateral pelvic wall through the obturator canal to supply the hip adductors and a patch of medial thigh skin. It is injured in pelvic surgery and childbirth.
- Sciatic nerveHY NerveThe largest nerve in the body (L4–S3), running from the buttock down the back of the thigh and dividing into the tibial and common fibular nerves. It supplies the hamstrings and everything below the knee except a strip of skin on the medial leg.
- Tibial nerveHY NerveLarger terminal branch of the sciatic nerve, running through the popliteal fossa and deep posterior leg to the sole. It supplies the plantarflexors and inverters and the skin of the sole, and is compressed in the tarsal tunnel.
Head & Neck
- Cervical plexusHY NerveNetwork of the C1–C4 ventral rami deep to sternocleidomastoid. It gives cutaneous branches to the neck and ear, the ansa cervicalis to the strap muscles, and most importantly the phrenic nerve (C3–C5) to the diaphragm.
- Common and internal carotid arteriesHY ArteryMain arteries of the head. Each common carotid divides at about C4 into external and internal carotids, and atherosclerosis at the bifurcation is a major cause of stroke and TIA.
- Extraocular musclesHY MuscleSix muscles that move each eye — four recti and two obliques — supplied by CN III, IV and VI (LR6 SO4, the rest 3). Testing them in the "H" pattern localizes cranial nerve palsies.
- Middle meningeal arteryHY ArteryBranch of the maxillary artery that enters the skull through the foramen spinosum to supply the dura and skull. Tearing of its anterior branch under the pterion causes an epidural hematoma.
- Muscles of facial expressionHY MuscleThin subcutaneous muscles derived from the second pharyngeal arch and supplied by the facial nerve (CN VII). Their pattern of weakness distinguishes a peripheral facial palsy (Bell palsy) from a stroke.
- Recurrent laryngeal nerveHY NerveBranch of the vagus that loops under the subclavian artery on the right and the aortic arch on the left, then climbs in the tracheoesophageal groove to supply the larynx. Injury causes hoarseness, a classic thyroidectomy complication.
- SkullHY BoneThe bones of the head — the neurocranium enclosing the brain and the viscerocranium forming the face. Pterion fractures, basilar skull fractures and infant fontanelles are the clinically important features.
Neuroanatomy
- Abducens nerve (CN VI)HY NerveSupplies 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)HY NerveMotor 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.
- Basal gangliaHY OrganDeep 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).
- CerebellumHY OrganCoordinates 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 arteries (ACA, MCA, PCA)HY ArteryThe three paired arteries that supply the cerebral hemispheres. Each territory gives a recognizable stroke syndrome; the MCA is the most commonly affected.
- Cerebral cortex and lobesHY OrganThe 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.
- Circle of WillisHY ArteryArterial 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.
- Corticospinal tractHY NerveMain 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.
- Cranial meninges and intracranial hemorrhageHY Space / regionThree 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.
- Dorsal column–medial lemniscus pathwayHY NerveAscending 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)HY NerveMotor 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) NerveMainly 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)HY NerveMotor nerve to the tongue. A lower motor neuron lesion makes the protruded tongue deviate toward the weak side, with atrophy and fasciculations.
- HypothalamusHY OrganSmall 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 capsuleHY OrganCompact 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 systemHY OrganNetwork 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 oblongataHY OrganLowest 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.
- MidbrainHY OrganUppermost 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.
- Oculomotor nerve (CN III)HY NerveSupplies 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) NerveSpecial 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)HY NerveCarries 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.
- Pituitary glandHY OrganMaster 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.
- PonsHY OrganMiddle 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.
- Spinothalamic tractHY NerveAscending 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.
- ThalamusHY OrganPaired 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.
- Trigeminal nerve (CN V)HY NerveLargest 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)HY NerveThinnest 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)HY NerveLongest 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.
- Vertebrobasilar systemHY ArteryThe 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.
- Vestibulocochlear nerve (CN VIII)HY NerveSpecial 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.