Neuroanatomy that keeps appearing in FCPS Part 1
Neuroanatomy questions are lesion questions: here is the deficit, where is the damage? Learn the tracts, the cord syndromes and the stroke patterns, and most questions answer themselves.
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Think like a neurologist on a ward round
Almost every neuroanatomy question is a localisation question. A patient has a set of findings; where is the lesion? That is exactly what you did when a senior asked you to examine a stroke patient on your medicine rotation.
Use the same three questions in the exam:
- Which pathways are affected? Motor, which sensations, which cranial nerves.
- Same side or opposite side? This tells you whether the lesion is above or below where each pathway crosses.
- What is spared? What is spared often localises better than what is lost.
The three tracts that decide most questions
| Tract | Carries | Crosses |
|---|---|---|
| Dorsal columns (medial lemniscus) | Fine touch, vibration, joint position sense | In the medulla |
| Lateral spinothalamic | Pain and temperature | Within one or two segments of entering the cord |
| Corticospinal (lateral) | Voluntary movement | At the medullary pyramids |
The anterior spinothalamic tract carries crude touch and pressure.
Romberg's test is a dorsal column test, not a cerebellar test. A patient with dorsal column loss is steady with eyes open and falls with eyes closed, because vision is doing the work position sense should do. A cerebellar patient is unsteady with eyes open too.
Cord syndromes
| Syndrome | Lost | Spared | Classic setting |
|---|---|---|---|
| Brown-Séquard (hemisection) | Same side: weakness and dorsal column loss. Opposite side: pain and temperature | Opposite side power | Stab wound to the back |
| Anterior cord | Power, pain and temperature below the level | Dorsal columns (vibration and position) | Anterior spinal artery occlusion, for example after aortic surgery |
| Central cord | Pain and temperature in a cape over the shoulders; arms weaker than legs | Dorsal columns | Syringomyelia; neck hyperextension in an older patient |
| Subacute combined degeneration | Dorsal columns and corticospinal tracts | Pain and temperature | Vitamin B12 deficiency |
| Cauda equina | Saddle anaesthesia, retention, bilateral leg symptoms, reduced reflexes | Upper motor neuron signs are absent | Large central lumbar disc |
The adult cord ends at L1 to L2. In the newborn it ends lower, around L3. That is why lumbar puncture is done at L3/L4 or L4/L5, and why the line joining the iliac crests (about L4) is the landmark.
Cauda equina is a surgical emergency. The exam answer is urgent MRI and decompression, not physiotherapy or a repeat review.
Brainstem strokes
| Syndrome | Artery | Same side | Opposite side |
|---|---|---|---|
| Lateral medullary (Wallenberg) | Posterior inferior cerebellar or vertebral | Facial pain and temperature loss, Horner's, ataxia, dysphagia and hoarseness (nucleus ambiguus) | Body pain and temperature loss |
| Medial medullary | Anterior spinal | Tongue deviates to this side (XII) | Hemiparesis and dorsal column loss |
Damage to the nucleus ambiguus gives dysphagia, hoarseness and a weak gag. It supplies the muscles of IX, X and the cranial part of XI.
Cranial nerve patterns worth knowing cold
- Third nerve palsy with a fixed, dilated pupil: compression, classically a posterior communicating artery aneurysm. The pupil fibres run on the outside of the nerve, so pressure hits them first. A sudden severe headache makes the aneurysm the urgent answer.
- Third nerve palsy sparing the pupil: diabetic or hypertensive microvascular damage to the centre of the nerve.
- Facial weakness sparing the forehead: upper motor neuron (stroke). The upper face has input from both hemispheres.
- Whole half of the face weak, including the forehead: lower motor neuron (Bell's palsy or a nerve lesion).
- Horner's syndrome: ptosis, miosis and loss of sweating on the same side, from damage anywhere along the sympathetic chain, including the neck and lung apex.
Cortex: one lesion, one sign
| Finding | Area |
|---|---|
| Slow, effortful, broken speech with good understanding (expressive aphasia) | Broca's area, inferior frontal gyrus of the dominant hemisphere |
| Fluent speech full of wrong and invented words, poor understanding (receptive aphasia) | Wernicke's area, posterior superior temporal gyrus |
| Fluent speech and good understanding but cannot repeat | Arcuate fasciculus (conduction aphasia) |
| Cannot recognise familiar faces | Fusiform gyrus |
| Cannot identify an object by touch with the eyes closed | Opposite parietal lobe |
| Ignores the left side of the world | Right parietal lobe |
The thalamus as a relay station
- VPL: body sensation.
- VPM: face sensation and taste.
- Lateral geniculate body: vision (think "L for light").
- Medial geniculate body: hearing (think "M for music").
Pure motor stroke
A hypertensive patient with sudden weakness of the face, arm and leg equally on one side, with no sensory loss and no cortical signs, has a lacunar infarct in the posterior limb of the internal capsule. The vessels are the lenticulostriate branches of the middle cerebral artery.
Visual pathway
| Field defect | Lesion |
|---|---|
| Loss in one eye | Optic nerve |
| Bitemporal hemianopia | Optic chiasm, classically a pituitary tumour |
| Homonymous hemianopia | Optic tract or the whole radiation on the opposite side |
| Upper quadrant ("pie in the sky") | Temporal lobe (Meyer's loop) |
| Lower quadrant | Parietal lobe |
Ventricles, CSF and bleeds
- CSF is made by the choroid plexus and absorbed through the arachnoid granulations into the dural venous sinuses.
- The most common cause of congenital obstructive hydrocephalus is aqueductal stenosis.
- The anterior horn of the lateral ventricle has the corpus callosum as its roof, the head of the caudate laterally and the septum pellucidum medially.
| Bleed | Vessel | Shape on CT | Story |
|---|---|---|---|
| Extradural | Middle meningeal artery | Biconvex (lens-shaped) | Blow to the side of the head, lucid interval, then deterioration |
| Subdural | Bridging veins | Crescent | Older patient or alcohol use, falls, slow confusion |
| Subarachnoid | Berry aneurysm | Blood in the cisterns | Sudden "worst ever" headache |
The middle meningeal artery runs under the pterion, where the skull is thinnest. A cricket ball to the side of the head is the classic way the question tells you this.
How to revise neuroanatomy
- Draw a cross-section of the cord and mark the three tracts and where each crosses. Do it daily for a week.
- Learn the cord syndromes table.
- Learn the two medullary strokes.
- Then work through lesion questions without looking at the options first. Name the site, then check.
The FCPS-1 Prep question bank has a large set of localisation questions with a sketch for each lesion pattern.
Read next: Anatomy high-yield · Physiology high-yield · Embryology high-yield
Frequently asked questions
Is neuroanatomy asked in both Medicine and Surgery groups?
Yes. Core neuroanatomy sits in Paper 1, which both groups take. Surgery candidates also see more applied head injury and spinal anatomy in Paper 2.
Which source is best for neuroanatomy?
A short clinical neuroanatomy review with diagrams, plus lesion-based questions. Large textbooks rarely help in the time you have.
What is the single highest-yield neuroanatomy topic?
The spinal tracts and where they cross. Most cord and brainstem questions depend on them.