LESIONS

A Guide to Localisation in Neurology

DEFINITIONS - A NEUROLOGY GLOSSARY

Neurology is terminology-heavy. People often find this hard. However, with the exception of eponyms, most terms are highly logical - the issue is just sheer volume, and lack of understanding of the meaning, although it doesn't help that some are Latin and many things have more than one name.

Here is a glossary to assist learners as they work through these cases - and assess neurology patients in the real world.

As much as I might like to see them gone, eponyms are also very common, both in clinical practice and in anatomy - and unfortunately, they're unavoidable. Since we're stuck with them, we might as well learn about the people they're named after, so I've added a short section on that at the end, for those interested - by no means 'core knowledge'!

Anatomical terms

General anatomical terms

Aperture - a small window in a structure.

Arcade - a series of arches forming a structure. There are some examples of this which have eponymous names, for example the arcades of Frohse or Struthers - both of which are relevant to nerve entrapment syndromes in the arm.

Arcuate - adjective meaning 'arched', for example the arcuate fasciculus in the caudal medulla - where sensory fibres decussate.

Canal - a narrow passage, usually like a tube or cylinder, and longer than a simple foramen (hole). Different things can pass through it. Below are some examples:

• Central canal - the CSF-containing channel within the spinal cord.
• Spinal canal - the hollow area within the vertebral column, containing the spinal cord.
• Optic canal - a tunnel in the sphenoid bone which the optic nerve passes through on its way to the chiasm
• Carotid canal - a tunnel in the sphenoid bone; the carotid artery passes through this to enter the cranial cavity.

Cavity - a large area containing organs, for example the cranial cavity.

Chiasm -an X-shaped crossing of structures, mainly the optic chiasm - which is often referred to as 'the chiasm'. Pre-chiasmatic and post-chiasmatic are adjectives used in lesions anterior or posterior to the optic chiasm.

Cistern - a CSF-containing space around the brainstem, for example the ambient, crural, and pre-pontine cistersns.

Colliculus - a small mound, usually formed by fibres, such as the facial, inferior and superior colliculi in the dorsal brainstem. The term means 'little hill'.

Commissure - a bundle of nerve fibres connecting both sides of the nervous system. Examples:

• Anterior commisure of the brain - connecting both hemispheres
• Anterior commisure of the spine - the crossing over of the spinothalamic tract, anterior to the gray matter

Decussation - a crossing over of nerve fibres. Many pathways feature this, connecting one side of the brain to the opposite side of the head or body. 'Decussate' is a verb meaning 'cross over'.

Fasciculus - a bundle of fibres (anglicised as 'fascicle'). This mainly is used for nerve fibres, particularly within brain, brainstem or spine parenchyma. Examples:

• The fascicular portion of a cranial nerve (fibres projecting from the nucleus, within the brainstem, and not yet in the nerve itself which is outside of the brainstem).

• The medial longitudinal fasciculus, a vertical bundle of fibres linking the nuclei of nerve VI (pons) with nerve III (midbrain), allowing binocular conjugate gaze.

Fissure - a separation of lobes or hemispheres of the brain. The great longitudinal fissure separates the two hemispheres, while the Sylvian fissure separates the temporal lobe from the frontal and parietal lobes.

Foramen - a hole, for example those in the skull in which structures (nerves, vessels and the brainstem) pass, or within the CSF ventricles (e.g. foramen on Monro). The plural is foramina.

Fossa - a hollow area that contains a structure. The cranial space is divided into three - the anterior, middle and posterior fossae.

Funiculus - similar to a fasciculus, but thicker - like a 'rope' or stalk. The spinal white matter is organised into these around the grey matter horns -

Ganglion - a group of neuronal cell bodies. The term is used for the peripheral nervous system, including cranial nerves - for example the trigeminal Ganglion.

Genu - this means 'knee', and is used for curved parts of a structure, for example in the corpus callosum or the internal capsule.

Gyrus - an area of grey matter cortex -

Infundibulum - a funnel-shaped structure, mainly the one connecting the pituitary to the hypothalamus.

Lamina - a flat structure, which may connect structures - for example in the vertebrae where the lamina links the spinous process with the pedicles.

Lemniscus - a band of nerve fibres, similar to a fasciculus. The main examples are the medial and lateral lemnisci, involved in tactile and auditory sensory information transport respectively.

Nucleus The region containing the cell bodies of neurons, for example those of each cranial nerve within the brainstem. Lesions in these are referred to as 'nuclear'.

Parasagittal - an adjective for a lesion in the midline between the two hemispheres, particularly tumours. The major one is meningioma, growing on the falx, and the classic presentation is with bilateral leg weakness, mimicking a cord lesion - and easily missed if the brain isn't scanned.

Pars - meaning 'part', for a small portion of something. For example the substantia nigra has a reticular (pars reticularis) and compact (pars compacta) part. The area of the inferior frontal gyrus that houses the expressive language (Broca) area has three pars - opercularis, triangularis and orbitalis. Pars may also refer to part of a sulcus - for example the pars marginalis in the marginal sulcus.

Pedicle - a small connecting segment, like a stalk - as found in the vertebrae.

Ramus - generally a projecting portion of a structure such as nerves (there are dorsal and ventral rami in the spinal nerves) and bones - e.g. the mandibular ramus.

Rostral - adjective meaning, 'at the front'. The nervous system is distinct from other parts of the body in that we use terms that apply to quadripedal animals, but we have an upright position. We use the term rostral mainly for brainstem anatomy in humans, and superior is an acceptable alternative.

Sinus - a hollow cavity whcih may contain air (e.g. the paranasal sinuses) or blood (the venous sinuses in the skull, formed between dural layers).

Somatotopic - an adjective referring to how parts of the nervous system are organised in relation to body parts they represent. The best examples are the motor and sensory homunculi. It also applies to deeper tracts, where there may be separation of fibres to/from the head, arm, trunk and leg (e.g. laterally as in the spinal cord, or anterior-to-posterior as in the internal capsule). Not everything is as simple as 'this area covers this part' - for example it is less clear how the thalamus and cerebellum are organised in somatotopic terms, in comparison to the homunculi. Clearly, somatotopic organisation is very important in localisation!

Stria - a line of nerve fibres. Striae is the plural. Example: the striae medullaris in the fourth ventricle, visible lines running horizontally which carry auditory information to the cerebellum.

Sulcus - a groove in the folded cortex, like a dip between two gyri - enough to separate them into anatomically discrete areas.

Tract - a pathway formed of nerve fibres running in a direction, for example the spinothalamic and optic tracts.

Trochlea - from the Greek for 'pulley'. The troclear nerve (IV) is so named as the superior oblique muscle has a sling-like loop (the trochlea) supporting it, attached to the roof of the orbit.

Trigone - a triangular section within a strucutre. Some examples include:

• Part of the lateral ventricle which protrudes laterally - also known as the atrium.
• The hypoglossal and vagal trigones - projections of the dorsal medulla which form triagnular mounds within the fourth ventricle

Tunnel - a passageway surrounded by connective tisuse. Tendons may pass through, but for our purposes, peripheral nerves also might, and can become trapped there. The commonest is carpal tunnel syndrome (median nerve, wrist). Another is cubital tunnel syndrome (ulnar nerve, elbow).

Uncus - Latin for 'hook'.

Uncinate - adjective for 'hooked'. There are uncinate processes in some vertebrae.

Ventral - adjective meaning, 'along the front'. The nervous system is distinct from other parts of the body in that we use terms that apply to quadripedal animals, but we have an upright position, so ventral really just means 'anterior' in humans. The other related terms are dorsal, caudal, rostral.

Ventricle - a fluid-filled cavity. In the brain there are several - two lateral ones, the third, and the fourth.

Specific anatomical ares

Various ones... Fissure, falx, tentorium, sylvian fissure, incisura, torcula, habenula , the ones in the 3rd ventricle, pineal...

Aqueduct - the CSF channel in the centre of the midbrain

Arcuate fasciculus - a white matter tract linking the receptive and expressive language areas.

Brachium conjunctivum - the superior cerebellar peduncle.

Calcarine sulcus - a dividing line between the upper and lower parts of the occipital lobe. Visual fibres terminate here, and those from the upper quadrant deposit on the cortex below the calcarine sulcus, vice versa for those from the lower quadrant. On an antero-posterior line, the more peripheral fibres deposit anteriorly, while those from the central part of vision deposit at the posterior pole.

Cavernous sinus - there are two of these, each formed between the two layers of dura (meningeal and periosteal) containing venous blood, lying either side of the pituitary fossa. Several structures pass through - the carotid artery, the sympathetic nerves, and nerves V1, V2, III, IV and VI. Lesions produce combinations of deficits in these - the 'full house' picture causes complete ophthalmoplegia and numbness of the V1 and V2 areas in the face.

Claustrum - a thin strip of grey matter in between the putamen and the insula.

Falx cerebri - a large sheet of dura in the great longitudinal fissure, separating the hemispheres.

Insula - a deep part of the cortex tucked inside the Sylvian fissure.

Internal arcuate fibres - the dorsal column-medial lemniscus pathway fibres reach the caudal medulla, synapse in the arcuate nucleus, then project the internal arcuate fibres, which decussate and ascend in the medial lemniscus.

Medial longitudinal fasciculus - a vertical bundle of fibres linking the nuclei of nerve VI (pons) with nerve III (midbrain), allowing binocular conjugate gaze.

Obex - the most caudal part of the 4th ventricle, below which it becomes the central canal of the spinal cord. The term is latin for 'barrier'.

Operculum - the term means 'lid' or 'cover'. This is an area where the frontal, temporal and parietal lobes lobes converge either side of the Sylvian fissure. The insular cortex is on the inner aspect of this - covered by the operculum.

Paramedian pontine reticular formation - a centre in the dorsal caudal pons involved in conjugate lateral gaze to the same side.

Restiform body - the inferior cerebellar peduncle.

Rostrum - an anterior, curved part of the corpus callosum. The term means 'beak'. It is below the genu, which is the most anterior part.

Tectum - the most dorsal part of the midbrain, posterior to the aqueduct. The inferior and superior colliculi are here. The adjective 'tectal' refers to this region, and 'pretectal' for the area just above this.

Tegmentum - the dorsal part of the upper brainstem (pons and midbrain), next to the CSF channel (fourth ventricle for pons, aqueduct for midbrain). It is clinically important as there are so many nuclei and tracts within it, so tegmental lesions produce deficits.

Torcula - also known as torcula Herophili after a Greek anatomist. A junction point where the superior sagittal sinus converges with several others - including the straight sinus (which drained the central, deep parts of the brain), the occipital sinus (draining the occipital area) and then the two transverse sinuses, which the blood empties into before leaving the intracranial zone (via the sigmoid sinuses and then jugular veins).

Trigeminal impression - a hollow zone in the petrous temporal bone's apex. The trigeminal ganglion sits here within Meckel's cave.

Uncinate fasciculus - a white matter tract linking the limbic (temporal) regions with the frontal lobe.

Eponymously-named anatomical structures

Arcade of Frohse - a membranous edge on the supinator muscle. The posterior interosseous nerve, a motor-only branch of the radial nerve, can become trapped against this, producing wrist and hand weakness (in extensor muscles only).

Arcade of Struthers - a band of connective tissue in the medial head of the triceps. It can sometime strap the ulnar nerve above the elbow.

Artery of (...) - there are many of these, with examples below. Some are normal structures, while others are variants that can cause unusual syndromes.

• Adamkiewicz - a major artery that feeds into the anterior spinal artery.
• Huebner - a recurrent (looping backwards) branch from the anterior cerebral artery that perfuses areas including the caudate head and anterior limb of the internal capsule.
• Percheron - a single supply to both dorsomedial thalami. Occlusion can produce coma and, in survivors, dementia.

Ciliospinal centre of Budge - part of the sympathetic tract in the C8-T2 spinal cord, where the first- and second-order neurons synapse. It's involved in pupillary dilatation - lesions cause Horner's

Circle of Willis - the central 'roundabout' at the base of the brain, with a single posterior input (the basilar artery, from both vertebrals) and bilateral anterior input (the internal carotids). The vessels perfusing the brain, brainstem and cerebellum all emerge from this.

Clarke's column - neurons in the spine involved in carrying proprioception from the legs

Dorello's canal - a small area next to the petrous temporal bone apex, which the abducens nerve (VI) passes through.

Foramen of Luschka - there are two of these CSF exit spaces, also known as lateral apertures - which project laterally out of the fourth ventricle. CSF leaves it and drains into the subarachnoid space.

Foramen of Magendie - a central hole in the posterior part of the fourth ventricle. CSF passes through it and drains into the cisterna magna - a large CSF space below the cerebellum.

Foramen of Monro - the name is singular, but there are two of these CSF channels, linking the two lateral ventricles with the third ventricle. They slope diagonally and inferiorly towards the centre.

Gasserian ganglion - the trigeminal ganglion.

Gruber's ligament - the petroclinoidal or petrosphenoidal ligament, which (as the name suggests) forms a band from the petrous temporal bone to the anteroir clinoid process on the sphenoid bone, and forms the roof of Dorello's canal. The abducens nerve (VI) passes below it, before entering the cavernous sinus.

Heschl's gyrus - part of the primary auditory cortex, hidden within the Sylvian fissure. The proper name is the transverse temporal gyrus.

Lissauer's tract - just before the axons carrying pain and temperature synapse in the grey matter, they rise 1-2 segments on the side of entry in Lissauer's tract, then enter the dorsal horn.

Meckel's cave - a pocket of dura folded back on itself, which the trigeminal ganglion sits in. It is not a complete encasement, unlike other structures such as the venous sinuses - it is more like a 'sleeve'.

Merkel corpusle - touch receptors in the skin which detect pressure

Meyer's loop - the inferior radiation of the second-order neurons in the visual pathway, distal to the lateral geniculate nucleus (thalamus). It travels in the temporal lobe and carries vision from the contralateral upper quadrant (from both eyes). It terminates in the occipital cortex below the calcarine sulcus.

Nodes of Ranvier - peripheral nerves have myelin sheaths, and the gaps in these are called nodes of Ranvier. The electrical signals jump across these, which is known as saltatory conduction

Nucleus of (...)

• Dieters - the lateral vestibular nucleus in the rostral medulla.
• Meynert - in the forebrain, producing acetylcholine which supplies the cortex.
• Edinger-Westphal - in the dorsal midbrain, near the periaqueductal gray area and oculomotor (III) nuclei - which sends pupil constricting signals as part of the pupillary light reflex
• Onuf - in the sacral parts of the cord (which are not in the sacral spine but the terminal parts at the low thoracic and upper lumbar vertebral levels). Involved in bladder, bowel and sexual functions.
• Raphe - lots of nuclei rather than one, lining the entire brainstem, producing serotonin (5HT).

Rexed laminae - the spinal cord grey matter is H shaped, and divided into 10 layers termed laminae

Rolandic cortex - the pre- and post-central gyri (motor and sensory strips)

Struthers' ligament - not everyone has this. A fibrous band in the distal humerus linking the supracondylar region to the medial epicondyle. The median nerve passes below it, so it can cause entrapment here - with a very proximal median nerve lesion, and a broad set of deficits as a result. (Note - this is distinct from the arcade of Struthers)

Sylvian fissure - this is the lateral fissure which separates frontal and parietal lobes (above and medial) from the temporal lobe (below and lateral).

Vein of (...)

• Galen - a deep vein draining the internal brain
• Labbé - a lateral vein over the temporal lobe, draining into the transverse sinus.
• Rosenthal - deep draining veins around the basal brain
• Trollard - a superficial vein over the brain's surface, draining the cortex into the superior sagittal sinus

Eponymous syndromes

Broca’s aphasia – lesion in the inferior frontal gyrus. Severe, non-fluent, expressive dysphasia, with broken, agrammatical sentences, difficulty saying words, and frequent phonemic paraphasic errors – but retained comprehension.

Horner's syndrome - features due to disruption any one of the three sympathetic neurons in a long pathway from the hypothalamus through brainstem, cervical and upper thoracic spinal cord, sympathetic chain, cervical ganglia and eventual output to the face, including the pupil and eyelid. The consequence is a constricted pupil (with the anisocoria most visible in the dark), a partial ptosis, and loss of facial sweating (though this part can be subtle or absent). Horner's has many causes - what helps localise the lesion is other co-occuring features (e.g. those of Wallenberg syndrome, or other cranial nerve palsies).

Wernicke’s aphasia – lesion in the superior temporal gyrus. Fluent but incomprehensible speech, with the patient unaware of the issue (they can't monitor their own speech), and completely unable to understand others.

Wallenberg's syndrome - a lateral rostral medullary lesion, usually infarct (in the PICA territory), takes out several structures - nuclei and tracts - in one move. Often the cerebellum is also affected. Vertebral artery dissection is an important cause. Features include:

• Horner's - descending sympathetic tract
• Ipsilateral facial loss of pain and temperature sensation - spinal trigeminal nucleus
• Contralateral body loss of pain and temperature sensation - spinothalamic tract (above decussation)
• Dysphagia - nucleus ambiguus
• Dysphonia - dorsal motor nucleus of X
• Vertigo - medial and lateral vestibular nuclei (and sometimes also the flocculonodular part of the cerebellum)
• Ipsilateral ataxia - inferior cerebellar peduncle

Signs

Eponymous signs and tests

Babinski sign - a cutaneous, not tendon, reflex. Stroking the lateral sole of the foot makes the big toe up and the others fan out. This indicates upper motor neuron damage. Be careful not to confuse a ticklish withdrawal reflex with this.

'Other' Babinski sign - in hemifacial spasm, the eyebrow elevates on the contracting side

Bell's phenomenon - closing the eyes forcefully leads to both eyes rolling up. This is a defensive response and is normal - we can't see it unless the eyelids are passively held open. In lower motor neuron facial paralysis it is evident when the person tries to close the eyes. In functional (not deliberate) or feigned (deliberate) unresponsive states, people resist passive eye opening, and if the lids are lifted Bell's phenomenon is evident.

Brudzinski's sign - passively flexing the neck causes hip and knee flexion in meningeal irritation (particularly infectious). As with Kernig's sign this is specific (if you see it it's suggestive), but not sensitive (most people with meningism won't have it).

Bruns nystagmus - damage in the lateral pons or medulla causes two effects - vestibular and cerebellar peduncle damage. The classic is a cerebello-pontine angle. Two types of nystagmus arise, seen in horizontal gaze at either side:

1. Cerebellar-type: coarse, slow, and gaze-evoked looking to the side of the lesion
2. Vestibular-type: fine, fast, and beating away from the lesion; most obvious when looking to the opposite side (Alexander's law)

Dix-Hallpike test - benign paroxysmal positional vertigo (BPPV) is due to crystal build-up in the semicircular canals, with specific head movements triggering attacks. The Dix-Hallpike test is one of several manouevers to induce an attack. The patient's head is turned outward then held somewhat upside down, and after a few seconds' latency nystagmus (upbeat, torsional) begins, accompanied by symptoms. The test is only positive with the nystagmus - the vertigo is not enough!

• Alexander's law - vestibular disease (especially neuritis) causes nystagmus with the slow phase towards the hypo-active side, as the intact side tonically pushes the eyes away from it. The fast phase is back to the intact side. When looking toward the intact side the nystagmus becomes more intense - this is Alexander's law, and is a useful clinical clue
• Argyll-Robertson pupil - the pupils don't constrict to light yet do during accomodation (fixation on a close target). Classic sign of late-stage neurosyphilis.
• Cogan's lid twitch sign - seen in myasthaenia. Looking down, then quickly shifting to primary position (looking ahead) with a saccade, the upper eyelid overshoots then drops a little. Subtle!

Chvostek's sign - low calcium causes tetany (neuromuscular hyperactivity). Tapping the side of the face near the jaw angle causes facial twitching.

• Hering's sign - in myasthaenia, when lifting an eyelid the other droops further. This is due to dual innervation. The examiner lifting one lid sends signals to the other to relax its activity, hence the drooping
• Hutchinson's pupil - a fixed, dilated pupil due to oculomotor (III) nerve compression from uncal herniation
• Marcus-Gunn pupil - a relative afferent pupillary defect
• Parkinson's sign - Horner's plus a VI palsy, due to cavernous sinus pathology

Froment's sign - we can normally pinch a sheet by adducting the thumb to the index finger. In ulnar neuropathy this is weakened, so the patient flexes the thumb to compensate, using the flexor pollicis longus muscle - innervated by the anterior interosseous nerve (median).

Gower's sign - proximal myopathy prevents people getting up from the ground, so they use their arms to form a base, then walk their hands back to help them stand.

Hoover's sign - a sign of functional weakness. It relies on showing voluntary weakness but intact involuntary strength, using a movement (hip flexion) that requires contralateral hip extension:

1. Hip extension is weak when tested directly ('try to push down on my hand')
2. When testing hip extension in the opposite leg, the weak leg now displays strong hip extension (involuntary/automatic)
3. Paralysis from a structural lesion would not display this. It is an example of internal inconsistency

Hoffman's sign - flicking the distal phalanx of the middle finger makes the thumb and index finger contract as if briefly pinching. A sign seen in upper motor neuron lesions, particularly cervical cord damage - but it can also be seen in healthy, anxious people (like many we see in clinic!)

Holmes rebound test - the patient holds their hands outstretched, and you push down and tell them to resist, then release. In cerebellar disease the arms rise up then rebound downward, due to loss of agonist-antagonist coordination.

Hutchinson's sign - a shingles vesicle on the tip of the nose predicts broader V1 involvement, which can threaten the eye. Spotting this should trigger very careful eye care to prevent blindness.

Kernig's sign - passively lifting the leg bent, then extending the knee, triggers pain. This is specific for meningeal irritation (particularly infectious) but not sensitive - meaning you'll not see it in most people but if you do see it, it's suggestive of meningitis.

Lasegue sign - passively flexing leg triggers radicular pain down the back of the leg. If this is the same pain the patient has been suffering, it supports radiculopathy, usually from a lateral disc prolapse affecting L5 or S1.

Lhermitte's sign - this is a symptom, not a sign, although you could also demonstrate it in clinic. Neck flexion causes electric shocks into the limbs and down the back. The best-known cause is demyelination but it can be caused by many forms of damage.

Myerson's sign - tapping the glabella causes us to blink, but we usually habituate (stop after a few taps). In Parkinson's this habituation is lost and blinking continues with further taps. This test can look somewhat rude so it is important to at least explain what you are about to do (even if you don't say what you expect to see, which could influence behaviour).

Romberg's sign - we rely on eyes, ears (vestibular signals) and feet (proprioception) to balance. We can function with only two of these but not one. Closing the eyes can expose a fault in either of the remaining two, with people losing balance if not supported. First described in syphilis in the pre-treatment era - dorsal column disease (tabes dorsalis) was a common feature

Tinel's test - tapping a nerve causes tingling distally. This is useful to provoke symptoms, particularly in median and ulnar entrapment neuropathies. It doesn't work for motor-only nerves (e.g. posterior interosseous), and with advanced entrapment neuropathy it can be negative as the nerve is dead.

Wartenberg's sign - ulnar neuropathy causes the little finger to naturally abduct from the ring finger. This seems confusing at first - the abductor digiti minimi (ADM) is an ulnar-innervated muscle - but the cause here is loss of adductor (lumbrical) action and unopposed action from the extensor digiti minimi, a radial-innervated muscle.

Other signs

Anisocoria - asymmetrical pupil sizes. This has many causes. In unconscious patients the main concern is life-threatening uncal herniation causing an oculomotor palsy.

Anosoagnosia - lack of awareness of a deficit. Examples include visual field defects the patient hasn't noticed as primary loss of vision, but instead notices the consequences (e.g. bumping into things). Another is lack of awareness of, or concern about, a weak limb.

Apraxia - issues performing a task that are not otherwise explained by any of the following - weakness, numbness, ataxia, confusion/cognitive impairment or other more 'primary' issues. Instead it's best thought of as a problem with complex performance of tasks, due to failure of parts of the brain involved in generation an action. Apraxia has various types, and they're often seen in neurodegenerative disorders. Subtypes include

• Ideational apraxia - inability to think of the steps in an action the patient previously knew and would be able to do automatically - e.g. make a cup of tea
• Ideomotor apraxia - inability to copy gestures, or mime an action (key in lock, brushing teeth...)
• Gait apraxia - a term some are moving away from, but refers to a shuffling, broad based gait pattern with tiny steps taken, as if the feet are 'stuck down' - also known as magnetic gait. Seen in hydrocephalus.
• Apraxia of speech - a pattern of disordered speech which is not dysarthria, dysphasia or dysphonia. Speech sounds clumsy, irregularly pronounced, at times stuttering and taking several attempts to get a word right. Can be seen in progressive supranuclear palsy.
• Orobuccal apraxia - issues performing actions with the mouth/cheek muscles, e.g. in eating or speech.
• Limb-kinetic apraxia - difficulty with learned limb functions, usually the right hand and due to a left parietal problem.

• Apraxia of eyelid opening - inability to open the eyes, not due to weakness (i.e. ptosis) or excess muscle activity (blepharospasm)
• Oculomotor apraxia - inability to voluntarily move the eyes to a target, e.g. by a saccade. The patient tends to have to blink and thrust their head to get the eyes to move. Seen in various diseases including Huntington's and some genetic ataxias.
• Dressing apraxia - difficulty putting clothes on. We can ask about this in the history, and test it by turning a patient's jacket inside out then asking them to put it on.
• Constructional apraxia - inability to draw shapes, e.g. a flower or house, because the patient cannot conceive of or plan how to approach this task

Asterixis - inability to maintain a static position, with tone being lost, then a myoclonic jerk to resume the initial position. This is best seen with outstretched hands. In various encephalopathies it can be seen, for example hypercapnoea, uraemia, or hyperammonaemia. It can also be seen unilaterally with brain damage, for example from stroke.

Dysarthria - slurring of words (an issue with articulation). When the slurring is so severe as to make speech incomprehensible, this is anarthria. This is distinct from dysphasia which is a language issue, not a speech one.

Dysphasia - impaired language ability. This presents with issues related to verbal (word-based, not specifically 'spoken'!) communication. There may be issues with speaking/writing/typing (expressive dysphasia), or understanding speech or written words (receptive dysphasia). If both are present this is 'mixed dysphasia'. Various subtypes exist depending on the impact on abilities including overall fluency, naming, repetition and comprehension.

Hypoalgesia - diminished but present pain sensation, which can be seen on pinprick testing. The patient detects it and can feel it as a sharp sensation (in contrast to analgesia) - it just feels less sharp than it normally would, which is most obvious when another region has normal sensation.

Floccilation - the random picking at clothing and sheets seen in delirious patients.

Inattention - When there are bilateral stimuli presented, only one is detected - the stimulus to the intact side of the brain extinguishes the other. In this situation there is no primary deficit in sensation itself - e.g. hemianopia - and a unilateral stimulus can be detected in the field that has inattention. It's only when bilateral stimuli come that the patient cannot detect one side. This applies to vision and touch, which are represented on one side of the brain only. It doesn't apply to sound, which has bilateral brain representation from each ear. Neglect is a related term but refers more to the syndrome or behaviours seen as a result - effectively 'ignoring' half of the world.

Inverted reflex - tapping a tendon does not elicit the usual reflex, as it is absent - yet paradoxically the antagonist muscles react and move the joint in the opposite direction. This happens due to hyperreflexia in the antagonist. It is seen with LMN damage at the reflex being tested, and UMN damage below it - e.g. tapping the biceps (C5) leads to triceps contraction (C7) - due to spinal cord damage.

Miosis - excessive pupil constriction.

Mydriasis - excessive pupil dilatation.

Nystagmus - repetitive movements of the eyes. They are not random but repetitive. The commonest pattern is jerk nystagmus with a slow drift off the target followed by a corrective saccade back to the original position. The direction of the saccade ('beating') defines the direction of the nystagmus - for example, right-beating or down-beat nystagmus. There are many different types of nystagmus.

Perseveration - continuing to perform an action after an instruction has ceased or things have moved on - for example, repeatedly sticking the tongue out after being told only to once, or continuing to talk about a topic as the assessor tries to change to another. Seen in various cognitive disorders including acute encephalopathies and fronto-temporal dementias.

Ptosis - drooping of one or both eyelids. This has many causes.

Reflex spread - UMN damage makes muscles hyper-reactive, and tapping a reflex may cause adjacent muscles to also contract as if the reflex has ‘spread’ or 'spilled over' into its neighbours - e.g. finger flexion (median, C7) when the brachioradialis (radial, C6) is tapped.

Strabismus - a squint; the eyes are not aligned normally. This can be seen as a developmental issue but can be aquired, for example through nerve palsies.

Synkinesis - as a facial palsy heals, there may be cross-wiring of branches, meaning that movement in one branch of the nerve stimulates movement in another. This is particularly seen with facial movements such as chewing or speech triggering blinking.

Symptoms

Ageusia - loss of taste sensation.

Alexia - inabilty to read. There are various subtypes.

• Surface alexia - inability to pronounce irregularly-spelled words. The patient reads them as if phonetically pronounced, e.g. 'pint' rhyming with 'mint'. Seen in anterior temporal lobe disease, particularly semantic dementia (a degenerative condition).
• Pure alexia - isolated inability to read, with preserved writing and speaking ability. Letters are recognised, but not words; the patient reads letter-by-letter, then sounds out the word (the way children learn to read) - e.g. 'C-A-T...cat'. It's due to disruption of input to an area of the brain involved in reading.

Allodynia - a normally painless stimulus becomes painful. If you've ever had sunburn, this is what bedsheets cause. In neurology it can reflect neuropathic pain, whether from nerve or spine damage, as well as thalamic disease.

Amnesia - memory loss. This can be for new events (anterograde amnesia) or previous ones (retrograde amnesia). It has many causes. In dissociative amnesia (a psychogenic response to trauma) people lose memory of large periods of their life, sometimes their entire autobiographical history.

Diplopia - double vision. If this is only present with both eyes open it's binocular - the eyes are not lining up properly. If it's still present with one eye open it's monocular - there may be a lens/focusing issue. If the patient has diplopia with both eyes open, then with only the right eye open, then with only the left eye open - this is bilateral monocular diplopia, and is usually functional.

Dysaesthesia - an unpleasant sensation, for example burning or itch.

Dyschromatopsia - altered or reduced colour vision. Can reflect optic nerve damage (e.g. neuritis) but also temporal lobe damage, particularly the right fusiform gyrus in the basal temporal lobe.

Dysphagia - impaired ability to swallow. This can be from neurological causes but can also be due to mechanical problems such as obstructive masses. Please don't confuse it with dyphasia!

Dysphasia - impaired language function. This isn't 'speech disturbance' - many who can't speak have intact language function, but dysphasia does interfere with spoken communication. It also interferes with written language. It can be expressive, receptive, or both.

Hallucination - an abnormal sensation in the absence of an actual stimulus, particularly auditory, visual, or olfactory. We don't really refer to simple tactile sensations such as paraesthesia as hallucinations, even though they are; we tend to use tactile hallucination to mean other sensations such as insects under the skin (formication).

Oculodynia - eye pain. It's quite common in a range of headaches, particularly migraine, but if there's pain moving the eye this can suggest optic neuritis.

Oscillopsia - jumping vision. This can happen for a few reasons. Nystagmus may cause it. Bilateral vestibular disease also can, when patients are walking on uneven ground - as the vestibulo-ocular relex is impaired, so they cannot hold focus as the head position constantly shifts.

Palinopsia - after-images. Moving images leave a trail, similar to a long-exposure photograph, or may persist in one place even after the object has moved. Sometimes patterns (for example on someone's clothes) are projected wherever the patient looks, for example onto walls.

Phantosmia - an olfactory hallucination. This has many causes. If brief, recurrent and stereotyped it can suggest focal seizures. If persistent, it can be due to migraines, as well as pregnancy.

Syndromes

There are too many of these to include, and many cause global or multi-site problems - so this is focused to anatomically relevant ones from a localisation perspective.

Facial colliculus syndrome – a lesion at the dorsal caudal pons, affecting the facial colliculus - a mound where the fascicle of VII runs round the nucleus of VI. The effect is inability to look to the affected side (conjugate gaze - both eyes) and lower motor neuron-pattern facial weakness.

Occipital condyle syndrome – pain on head turning, associated with an XII palsy. Cancer is a major cause as well as tuberculosis.

Pathological terms

Tumefactive - a lesion (or multiple) that is not a tumour but has a space-occupying effect (mass effect on adjacent structures, surrounding oedema) and resembles a tumour - typically with round, sizeable lesions that often have contrast enhancement on imaging. This term is particularly used in inflammatory lesions. Tumefactive multiple sclerosis is an example.

Myelitis – inflammation of the spinal cord (inflammatory myelopathy)

Myelopathy -spinal cord disease, of any kind - though 'myelopathy' is often used to mean ‘compressive cervical myelopathy’, usually due to discs or other degenerative pathologies.

Myeloneuropathy -combination of cord and peripheral nerve disease (e.g. B12 deficiency)

Radiculitis – inflammation at a root (e.g. from infection such as Lyme disease)

Radiculopathy - compression of a root, by any cause (though often used to imply a disc prolapse)

Spondylolisthesis - anterior slippage of one vertebral body on top of another

Spondylosis - age-related degeneration of the vertebral column (including disc prolapse, osteophytes, facet joint hypertrophy)

Historical figures with eponyms (for interest)