The nervous system

Richard Davenport

Hadi Manji

Anatomy and physiology 120

The history 120

Common presenting symptoms 122

Past medical history 123

Drug history 124

Family history 124

Social history 124

The physical examination 124

Assessment of conscious level 124

Meningeal irritation 124

Speech 125

Dysphasias 125

Cortical function 126

Cranial nerves 127

Olfactory (I) nerve 127

Optic (II), oculomotor (III), trochlear (IV) and abducens (VI) nerves 128

Trigeminal (V) nerve 128

Facial (VII) nerve 130

Vestibulocochlear (VIII) nerve 131

Glossopharyngeal (IX) and vagus (X) nerves 131

Accessory (XI) nerve 133

Hypoglossal (XII) nerve 133

Motor system 133

Anatomy 133

Stance and gait 134

Inspection and palpation of the muscles 136

Tone 137

Power 138

Deep tendon reflexes 139

Primitive reflexes 141

Coordination 141

Sensory system 142

Anatomy 142

Common presenting symptoms 143

Sensory modalities 144

Peripheral nerves 146

Median nerve 146

Radial nerve 146

Ulnar nerve 146

Common peroneal nerve 147

Lateral cutaneous nerve of the thigh 147

Interpretation of the findings 147

Investigations 147

Initial investigations 147

Specific investigations 149

OSCE example 1: Headache history 149

OSCE Example 2: Tremor 149

Integrated examination sequence for the nervous system 150

120 • The nervous system

The history

For many common neurological symptoms such as headache,

numbness, disturbance/loss of consciousness and memory loss,

the history is the key to diagnosis, as the examination may be

either normal or unhelpful. Some symptoms, including loss of

consciousness or amnesia, require an additional witness history;

make every effort to contact such witnesses.

Remember the two key questions: where (in the nervous

system) is the lesion and what is the lesion?

Neurological symptoms may be difficult for patients to describe,

so clarify exactly what they tell you. Words such as ‘blackout’,

‘dizziness’, ‘weakness’ and ‘numbness’ may have different

meanings for different patients, so ensure you understand what

the person is describing.

Ask patients what they think or fear might be wrong with

them, as neurological symptoms cause much anxiety. Patients

commonly research their symptoms on the internet; searches

on common benign neurological symptoms, like numbness or

weakness, usually list the most alarming (and unlikely) diagnoses

such multiple sclerosis, motor neurone disease or brain tumours

first, and almost never mention more common conditions such

as carpal tunnel syndrome or functional disorders.

Time relationships

The onset, duration and pattern of symptoms over time often

provide diagnostic clues: for example, in assessing headache

(Box 7.1) or vertigo (see Box 9.3).

Ask:

• When did the symptoms start (or when was the patient

last well)?

• Are they persistent or intermittent?

• If persistent, are they getting better, getting worse or

staying the same?

Anatomy and physiology

The nervous system consists of the brain and spinal cord (central

nervous system, CNS) and the peripheral nerves (peripheral

nervous system, PNS). The PNS includes the autonomic nervous

system, responsible for control of involuntary functions.

The neurone is the functional unit of the nervous system. Each

neurone has a cell body and axon terminating at a synapse,

supported by astrocytes and microglial cells. Astrocytes provide

the structural framework for the neurones, control their biochemical

environment and form the blood–brain barrier. Microglial cells

are blood-derived mononuclear macrophages with immune and

scavenging functions. In the CNS, oligodendrocytes produce

and maintain a myelin sheath around the axons. In the PNS,