Overview

Definitions

Some definitions of terms used in neurology are:

  • Neuropathy – disorders of peripheral nerves
  • Mononeuropathy – affecting one nerve
  • (Symmetrical) polyneuropathy – symmetrical nerves affected on both sides
  • Mononeuritis multiplex – 2 or more nerves affected in different discrete areas of the body
  • Myelopathy – disorders of the spinal cord itself
  • Radiculopathy – disorders of nerve roots
  • Myelitis – focal or diffuse inflammation of the spinal cord
  • Myeloradiculopathy – disorders of the spinal cord, nerve roots, and nerves
  • Encephalopathy – disorders of the brain

An Approach to Neurological Symptoms

Overview

Localisation is the process which uses the following to find the likely area a neurological lesion is present:

  • Subjective evidence – the clinical history
  • Objective evidence – the physical examination

This helps narrow down what investigations are indicated and where any imaging should be performed. For example, a lower motor neurone lesion would not show abnormalities on brain imaging.

The three main questions to ask are:

  • What is the timeline and progression like?
  • Where is this lesion?
    • Is it the central nervous system?
      • Upper motor neurones (UMNs) and/or lower motor neurones (LMNs)
    • Or is it the peripheral nervous system?
      • LMNs more likely
      • UMNs less likely, unless an element of the anterior corticospinal tract is affected, as UMNs in this tract decussate in the spinal cord down to the end of the thoracic region.
  • What type of neurological pathology is this?

What is the timeline and progression like?

The onset and timeline can help narrow down the diagnosis. In general if symptoms:

  • Emerge within seconds–minutes:
    • Suggest a vascular cause (e.g. stroke, intracranial bleed) or epilepsy
  • Emerge within minutes–hours:
  • Emerge over days and last for weeks before improving, and wax and wane:
  • Slowly progressing over weeks–months:
    • Suggest space–occupying lesions (e.g. intracranial tumours)
  • Slowly progressing over months-years:

Where is the lesion?

In general:

  • UMN signs involve the central nervous system (CNS) (brain and spinal cord)
  • LMN signs involve the peripheral nervous system (nerves, neuromuscular junctions, and muscles)
  • Both UMNs and LMNs can cause sensory problems

As a general rule of thumb:

  • CNS pathology may have both UMN and LMN signs
  • Peripheral nervous system pathology may only have LMN signs
    • UMN signs are still possible due to anterior corticospinal tract fibres decussating in the spinal cord towards the bottom of the thoracic region

UMNs and LMNs are discussed in more detail in Upper Motor Neurones, Lower Motor Neurones, and Descending Tracts.

An example of applying this would be between motor neurone disease (MND, e.g. amyotrophic lateral sclerosis) and a peripheral neuropathy (e.g. Guillain-Barré syndrome, GBS). MND has both LMN and UMN signs, therefore, it is likely to primarily be a CNS problem, whereas GBS typically only has LMN signs, therefore it is likely to primarily be a peripheral nervous system problem.

What type of neurological pathology is this?

Is it:

  • Focal?
    • Single and well-defined lesions in a specific region
    • For example, a left median nerve palsy causing left carpal tunnel syndrome
    • Generally unilateral, but may be bilateral
  • Diffuse?
    • Widespread dysfunction of a part of the nervous system
    • For example, numbness in a glove-and-stocking distribution in diabetic neuropathy
    • Generally bilateral, but may be unilateral if one side is injured faster than the other (e.g. the degeneration of the substantia nigra can be worse on one side than the other in Parkinson’s disease)
  • Multifocal?
    • Multiple focal lesions at different discrete locations, such as mononeuritis multiplex seen in diabetes mellitus or vasculitis.

Upper and Lower Motor Neurone Signs

Overview

These are discussed in more detail in Upper Motor Neurones, Lower Motor Neurones, and Descending Tracts: The pyramidal tracts.

Upper Motor Neurone Signs

Upper motor neurone (UMN) signs may include:

  • Negative symptoms:
    • Weakness
    • Decreased control
    • Easy fatiguability
  • Positive symptoms:
    • Spasticity – velocity-dependent increased tone to passive stretch
    • Clonus – rhythmic, involuntary muscle contractions when abrupt muscle stretch is applied
    • Hyperreflexia – brisk reflexes
  • Pathological reflexes:
    • The Babinski sign: stroking the sole of the foot leads to the extension of the large toe and fanning of the other toes – a positive Babinski sign
    • The Hoffman sign: holding the patient’s middle finger and flicking the fingernail downward leads to flexion and adduction of the thumb – a positive Hoffman sign

Most cranial nerves are bilaterally innervated. When both UMNs are damaged, the following may be seen:

  • Dysphagia
  • Dysarthria
  • A brisk jaw-jerk reflex
  • Tongue spasticity
  • Pseudobulbar affect – emotional imbalance (e.g. excessive crying or laughing)

The exceptions to this are cranial nerves VII (the facial nerve) and XII (the hypoglossal nerve):

  • CN VII:
    • Unilateral UMN lesions result in a lower facial droop away from the side of the lesion
    • The upper half is unaffected as it is bilaterally innervated
    • LMN lesions would affect the ipsilateral side and involve both the upper and lower face
    • A patient presenting with a UMN lesion of the face, where only the lower face is affected, should raise suspicion of stroke
  • CN XII:
    • Unilateral UMN lesions result in tongue deviation away from the side of the lesion

The cranial nerves and their lesions are discussed in more detail in Cranial Nerves.

Lower Motor Neurone Signs

Lower motor neurone (LMN) lesions have the following signs:

  • Decreased reflexes – reflexes may be absent
  • Decreased tone – muscles are weak or may be floppy
  • Muscle atrophy – muscles are wasting/thinning
  • Fasciculations – involuntary, rapid muscle twitches
  • Flaccid paralysis – paralysis and decreased tone

Since LMNs do not decussate, they cause ipsilateral signs.

Gait Signs

Hemiplegic gait

A hemiplegic gait is caused by neurological disorders (such as stroke) which result in hemiplegia (unilateral weakness and spasticity).

Patients with hemiplegia have spastic upper limb flexion and lower limb extension. Since the lower limb is extended, patients have to circumduct their leg when walking to prevent their foot from dragging on the ground.

Causes include:

  • Strokes
  • Tumours
  • Trauma
  • Degenerative changes
  • Vasculitis

Diplegic (scissor) gait

The hips and knees are flexed and abducted (bringing them together) whilst the ankles are extended and internally rotated.

Both knees are forced together, and to compensate, the patient circumducts both legs when walking.

Causes include brain injuries during birth such as spastic cerebral palsy.

Parkinsonian (festinating) gait

Patients with a Parkinsonian gait tend to start slow when walking as if they are ‘stuck in place’ and take small shuffling steps.

Other features include:

  • Reduced swinging of the arms when walking
  • Stooped posture due to a flexed neck and trunk
  • Slow turning and impaired balance on turning due to postural instability
  • Causes include Parkinson’s disease and Parkinson’s plus syndromes.

Hyperkinetic gait

Involuntary movements such as grimacing and choreiform movements in the upper and lower limbs (e.g. writhing) are seen.

Causes include Huntington’s disease and Wilson’s disease.

Ataxic gait

The gait is broad-based and unsteady. It can be divided into:

  • Cerebellar ataxia – due to cerebellar lesions:
    • If the lesion is unilateral, patients veer towards the side of the lesion
    • Turning is difficult
    • Causes include any damage to the cerebellum (e.g. alcohol, phenytoin, stroke, tumours etc.)
  • Sensory ataxia – due to impaired proprioception (e.g. damage to the dorsal columns):
    • Feet slam hard on the floor and there may be high stepping
    • Patients use vision to compensate for the loss of proprioception
    • Romberg’s test is positive

Causes include vitamin B12 deficiency

Neuropathic (high-stepping) gait

Seen in patients with lesions to the muscles in the distal lower limb, usually the dorsiflexor muscles of the foot leading to foot drop. Patients take higher steps when walking to prevent their foot from dragging on the ground.

Myopathic (Trendelenburg) gait

Seen in patients with weak hip abductor muscles. When walking, the pelvis drops to the unaffected side. Patients waddle by flexing their trunk away from the affected hip and swinging the other leg.

Antalgic gait

Seen in patients with pain in the affected limb. An affected patient may put less weight on the affected limb resulting in a limping appearance.

Marche à petit pas

Translates to “gait with little steps”. This is similar to a Parkinsonian gait however there is no stooping and reduced arm swing. Patients take small steps with an upright stance.

Causes include bifrontal lesions.

Magnetic gait

Patients walk as if they are ‘stuck to the floor’ with broad-based short steps with slow and unsteady turns.

Causes include normal pressure hydrocephalus. 

Coordination Signs

Ataxia

Ataxia describes a lack of voluntary coordination of muscles and can present as gait abnormalities, speech pattern abnormalities and abnormal eye movements including nystagmus. There are three types of ataxia:

  • Cerebellar ataxia – dysfunction of the cerebellum
    • Distinguished from other types by the presence of speech and oculomotor signs
  • Sensory ataxia – dysfunction of proprioception sense (e.g. lesions in the dorsal columns)
  • Vestibular ataxia – dysfunction of the vestibular system

Unilateral cerebellar lesions can cause ipsilateral signs. can be remembered using the acronym DANISH:

  • Dysdiadochokinesia (inability to perform quick, alternating movements) and dysmetria (under-/overshooting of an intended position of a limb)
  • Ataxia:
    • Cerebellar hemisphere lesions cause limb ataxia (clumsiness and incoordination of the upper limbs)
    • Cerebellar vermis lesions cause gait ataxia
  • Nystagmus (horizontal)
  • Intention tremor (a tremor during a directed motor movement, worsening before reaching the endpoint)
  • Scanning dysarthria (words broken up into syllables with noticeable pauses, such as saying walk (pause) ing, rather than walking) and slurred speech
  • Hypotonia

Sensory ataxia is different to cerebellar ataxia due to the presence of near-normal movement and coordination when the patient can see what they are doing. Closing the eyes effectively removes vision and this compensation, leading to worsening ataxia and a positive Romberg’s sign. Features include:

  • Unaffected speech
  • Unaffected eye movements
  • Impaired vibration sense – due to dorsal column lesions
  • Deep tendon reflexes may be absent

Vestibular ataxia presents with vertigo, nausea, and vomiting. Speech and oculomotor signs are not seen.

Pronator drift

The patient is asked to raise both arms to the level of the shoulder with the elbows extended and the palms facing upwards, fingers spread wide, and the eyes closed. The arms may pronate and drift downwards.

This tests UMN lesions. If a person has a positive pronator drift sign, there is a lesion in the contralateral cortex. It occurs because the supinator muscles are weaker than the pronator muscles.

Asterixis

Also known as a flapping tremor, asterixis is seen when a patient is asked to extend their arms with their eyes closed, dorsiflex their wrists, and spread their fingers. A flapping motion of the hands may be seen.

This is seen in hepatic encephalopathy, uraemic encephalopathy, and hypercapnia.

Romberg’s test

This is used to differentiate between sensory and cerebellar ataxia. The patient is asked to stand with both feet together and close their eyes:

  • Positive Romberg – the patient starts swaying or swaying increases
    • Suggests sensory ataxia as closing the eyes removes visual compensation
    • Falling sideways can suggest vestibular ataxia, patients fall towards the side of the lesion
  • Negative Romberg – the patient’s swaying does not increase
    • The patient may not be able to do this to start with
    • Swaying even with the eyes open suggests cerebellar ataxia

Abnormal Movement Signs

Athetosis

Athetosis describes involuntary writhing movements of the fingers, hands, toes, and feet. This occurs due to lesions in the corpus striatum (a nucleus in the basal ganglia of the forebrain).

Athetosis may occur in Huntington’s disease or Sydenham chorea.

Tremor

Tremors are involuntary rhythmic muscle contractions. These are discussed in more detail in Tremor: Assessment and Differential Diagnoses.

Fasciculations

Colloquially described as muscle twitching, these are involuntary muscle contractions and relaxations. They may be a sign of an LMN lesion, however, they may also be benign.

Posturing Signs

Abnormal posturing

This describes involuntary flexion/extension of the muscles in the arms and legs suggesting severe brain injury, such as cerebral herniation. If one set of muscles is non-functioning, the other set takes over. The two types of abnormal posturing are:

  • Decorticate posturing:
    • Flexion of the elbow, wrist, and fingers, with adduction and internal rotation of the shoulder
    • Extension and internal rotation of the lower limbs and extension of the knee and plantarflexion of the feet
    • Suggests damage above the level of the red nucleus (at the level or above the midbrain) 
  • Decerebrate posturing:
    • Extension of the elbow, pronation of the forearm, flexion of the fingers, and adduction and internal rotation of the shoulder
    • Extension and internal rotation of the lower limbs and extension of the knee and plantarflexion of the feet
    • Suggests damage below the level of the red nucleus (at the level of or below the midbrain)

Progression from decorticate posturing to decerebrate posturing suggests uncal or tonsilar brain herniation. Eventually, if the lower pons and upper medulla are involved, the patient loses all tone and becomes flaccid.

See Brain Herniation for more information.

Spasm

Spasms describe sudden involuntary muscle contractions.

Trismus

Also known as lockjaw, this describes pain and restriction when opening the mouth due to a muscle spasm.

This may be seen in a peritonsillar abscess (quinsy) or tetanus.

Paralysis Signs

Flaccid paralysis

Flaccid paralysis describes weakness/paralysis and reduced muscle tone. This is associated with LMN lesions.

This may be seen in acute polio and botulism.

Monoplegia, diplegia, paraplegia, hemiplegia, triplegia, tetraplegia

  • Monoplegia describes paralysis in a single limb
  • Diplegia describes paralysis affecting symmetrical sides of the body (e.g. paralysis of both sides of the face)
  • Hemiplegia describes complete paralysis unilaterally (one side of the body)
  • Paraplegia describes paralysis in the lower extremities
  • Triplegia describes paralysis in three limbs
  • Tetraplegia/quadriplegia describes paralysis in all four limbs due to lesions in the cervical spinal cord

Weakness and Sensory Signs

Hemiparesis

Hemiparesis describes unilateral weakness. Hemiplegia describes complete unilateral paralysis.

Paraesthesia

Aesthesia describes the normal ability to experience sensation and perception. Paraesthesia describes abnormal skin sensations such as numbness, tingling, prickling, chilling etc.

‘Pins and needles’ are a type of paraesthesia and formication, the sensation of insects crawling on the skin.

Upper Limb Nerves and Signs

Musculocutaneous nerve

  • Roots:
    • C5-C7
  • Sensory function:
    • Lateral forearm
  • Motor function:
    • Biceps brachii – elbow flexion and supination
  • Signs and symptoms of lesions:
    • Sensory loss/motor deficits
  • Causes of lesions:
    • Usually injured with brachial plexus

Long thoracic nerve

  • Roots:
    • C5-C7
  • Sensory function:
    • n/a
  • Motor function:
    • Serratus anterior
  • Signs and symptoms of lesions:
    • Winged scapula
  • Causes of lesions:
    • Injuries to the ribs

Axillary nerve

  • Roots:
    • C5, C6
  • Sensory function:
    • Supplies lower deltoid over the “regimental badge area”
  • Motor function:
    • Innervates deltoid muscle – shoulder abduction
  • Signs and symptoms of lesions:
    • Deltoid atrophy and impaired abduction
  • Causes of lesions:
    • Humeral head fracture or dislocation 

Radial nerve

  • Roots:
    • C5-C8
  • Sensory function:
    • Posterior forearm
    • Dorsal lateral 3.5 digits
  • Motor function:
    • Innervates forearm extensor muscles
  • Signs and symptoms of lesions:
    • Wrist drop
  • Causes of lesions:
    • Fracture of the midshaft of the humerus

Median nerve

  • Roots:
    • C6-T1
  • Sensory function:
    • Palmar lateral 3.5 digits
  • Motor function:
    • Thenar muscles
  • Signs and symptoms of lesions:
    • Lesion at wrist: features of carpal tunnel syndrome
    • Lesion at the elbow: loss of pronation and weak wrist flexion

Ulnar nerve

  • Roots:
    • C8-T1
  • Sensory function:
    • Palmar side of the medial 1.5 digits
  • Motor function:
    • Intrinsic hand muscles except for the thenar muscles and two lateral lumbricals
  • Signs and symptoms of lesions:
    • Patient cannot grip paper between fingers – positive Froment’s sign
  • Causes of lesions:
    • Fracture of the medial epicondyle

Erb’s palsy

  • Due to damage to C5-C6
  • Arm held in “waiter’s tip” position – adducted and internally rotated with the forearm pronated, with the hand and wrist flexed

Klumpke’s palsy

  • Due to damage to C8-T1
  • Associated with Horner’s syndrome
  • Usually secondary to complicated deliveries in pregnancy e.g. shoulder dystocia

Lower Limb Nerves and Signs

Femoral nerve

  • Roots:
    • L2-L4
  • Sensory function:
    • Anteromedial thigh and lower leg
  • Motor function:
    • Knee extension
    • Thigh flexion
  • Signs and symptoms of lesions:
    • Loss of sensation
    • Loss of knee extension/thigh flexion
  • Causes of lesions:
    • Hip and pelvic fractures

Obturator nerve

  • Roots:
    • L2-L4
  • Sensory function:
    • Medial thigh
  • Motor function:
    • Thigh adduction
  • Signs and symptoms of lesions:
    • Impaired thigh adduction
  • Causes of lesions:
    • Anterior hip dislocation

Sciatic nerve

  • Roots:
    • L4-S3
  • Sensory function:
    • n/a
  • Motor function:
    • Innervates posterior thigh muscles – knee flexion
  • Signs and symptoms of lesions:
    • Impaired knee flexion
  • Causes of lesions:
    • Compression of the sciatic nerve can cause radicular pain

Superior gluteal nerve

  • Roots:
    • L4, L5, S1
  • Sensory function:
    • n/a
  • Motor function:
    • Innervates some gluteal muscles – hip abduction
  • Signs and symptoms of lesions:
    • Positive Trendelenburg sign
    • Impaired hip abduction
  • Causes of lesions:
    • Pelvic fracture
    • Posterior hip dislocation

Inferior gluteal nerve

  • Roots:
    • L5, S1, S2
  • Sensory function:
    • n/a
  • Motor function:
    • Innervates gluteus maximus muscles – hip extension and lateral rotation
  • Signs and symptoms of lesions:
    • Impaired hip extension and lateral rotation
    • Difficulties getting out of a chair or jumping

Tibial nerve

  • Roots:
    • L4-S3
  • Sensory function:
    • Innervates posterolateral leg, lateral foot and sole
  • Motor function:
    • Foot plantarflexion
    • Foot inversion
    • Intrinsic foot muscles
  • Signs and symptoms of lesions:
    • Impaired foot sensation
    • Impaired plantarflexion/inversion
  • Causes of lesions:
    • Posterior knee dislocation

Common peroneal nerve

  • Roots:
    • L4, L5, S1, S2
  • Sensory function:
    • Lower lateral leg
    • Dorsum of the foot
  • Motor function:
    • Foot dorsiflexion and eversion
  • Signs and symptoms of lesions:
    • Foot drop
  • Causes of lesions:
    • Fibular neck fracture

Lateral cutaneous nerve of the thigh

  • Roots:
    • L2, L3 
  • Sensory function:
    • Lateral thigh
  • Motor function:
    • None
  • Signs and symptoms of lesions:
    • Meralgia paraesthetica
    • Paraesthesia (numbness, tingling, or pain) in the outer thigh
  • Causes of lesions:
    • Tight fitting clothing

Nervous System Tracts: A Summary

Overview

In general, lesions before decussation lead to contralateral signs and symptoms. Lesions after decussation lead to ipsilateral signs and symptoms.

Ascending tracts

Sensory tracts:

  • Conscious tracts:
    • Dorsal column-medial lemniscus pathway – decussates in the medulla:
      • Fine touch, proprioception, and vibration
  • Anterolateral system – both decussate in the spinal cord
    • Anterior spinothalamic tract
      • Crude touch and pressure
    • Lateral spinothalamic tract
      • Pain and temperature

Descending tracts

Motor tracts:

  • Pyramidal tracts – voluntary control of muscles in the body and face:
    • Corticospinal tract – decussates in the medulla
    • Corticobulbar tract – decussates above cranial nerve nuclei
  • Extrapyramidal tracts – dopamine antagonism may cause extrapyramidal side effects:
    • Acute dystonic reactions
    • Akathisia
    • Parkinsonism
    • Tardive dyskinesia

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