Neurology is the medical specialty concerned with the nervous system, including the brain, spinal cord, peripheral nerves, neuromuscular junctions and muscles as they relate to neurological disease. Neurologists diagnose and manage disorders involving movement, sensation, cognition, consciousness, language, coordination, autonomic function and neuromuscular activity. Major neurological conditions include stroke, epilepsy, migraine, multiple sclerosis, Parkinson's disease, dementia syndromes, peripheral neuropathies, motor neurone diseases, neuromuscular disorders and disorders of the spinal cord.
The nervous system integrates sensory information, generates motor responses, regulates internal physiological functions and supports cognition and behaviour. Neurological disease can therefore produce highly varied symptoms, from weakness or numbness to seizures, visual disturbance, memory impairment or abnormalities of speech and movement. Neurology overlaps with neurosurgery, psychiatry, rehabilitation medicine, neuroradiology, neurophysiology, genetics and many other specialties.
The nervous system consists broadly of the central nervous system and peripheral nervous system. The brain and spinal cord form the central nervous system, while cranial nerves, spinal nerves and peripheral nerves form major components of the peripheral system. Neurons transmit electrical signals and communicate through synapses using neurotransmitters and other signalling mechanisms, while glial cells provide structural, metabolic, insulating and immune-related functions.
Myelin, produced by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system, enables rapid saltatory conduction along many axons. Different brain regions support partially specialised functions, although complex functions such as language, memory and executive control depend on distributed networks. Neurological symptoms can therefore provide clues to anatomical localisation, with the pattern of deficits helping clinicians determine whether pathology is likely to involve the cortex, brainstem, cerebellum, spinal cord, peripheral nerve, neuromuscular junction or muscle.
Neurological diagnosis begins with detailed history and neurological examination. Examination can assess mental status, cranial nerves, motor strength, muscle tone, reflexes, coordination, gait, sensation and other functions. The distribution and combination of abnormalities can help localise a lesion before imaging or laboratory testing is performed. For example, a pattern affecting one side of the body may suggest a central lesion, while length-dependent sensory loss may suggest a peripheral neuropathy.
However, localisation is not always straightforward because diseases can affect multiple nervous-system regions simultaneously. Neurological history also pays particular attention to time course: sudden onset suggests different mechanisms from symptoms developing over hours, weeks or years. Episodic, progressive, relapsing or fluctuating patterns can similarly narrow diagnostic possibilities.
Stroke occurs when blood flow to part of the brain is interrupted or when a cerebral blood vessel ruptures and causes bleeding. Ischaemic stroke is usually caused by arterial occlusion, whereas haemorrhagic stroke results from intracranial bleeding. Brain tissue is highly dependent on continuous oxygen and glucose delivery, so prolonged interruption of blood flow can produce irreversible neuronal injury.
Sudden weakness, facial asymmetry, speech disturbance, visual loss, severe imbalance or other acute neurological deficits require urgent assessment because some treatments are time-dependent. Brain imaging distinguishes haemorrhage from many forms of ischaemic injury, while vascular imaging and cardiac assessment can help identify the underlying mechanism. Secondary prevention depends on the cause and can involve antithrombotic treatment, blood-pressure control, lipid management, diabetes management, smoking cessation and treatment of atrial fibrillation or other relevant conditions.
Epilepsy is a neurological disorder characterised by a persistent predisposition to epileptic seizures, which result from abnormal excessive or synchronous neuronal activity. A seizure is an event, whereas epilepsy is a disorder defined by a tendency to recurrent unprovoked seizures or an equivalent recognised clinical framework. Seizures can be focal, originating within networks initially limited to one cerebral hemisphere, or generalised, involving bilateral networks from the outset.
Clinical manifestations vary widely and can include altered awareness, abnormal movements, sensory experiences, autonomic symptoms or behavioural changes. Electroencephalography can provide evidence of abnormal electrical activity but a normal recording does not necessarily exclude epilepsy. Treatment depends on seizure type, cause, age, comorbidities and reproductive or medication considerations and may involve antiseizure medicines, surgery, neurostimulation or specialised dietary approaches in selected cases.
Neurodegenerative diseases involve progressive dysfunction or loss of specific neuronal populations and neural networks. Parkinson's disease is associated particularly with degeneration of dopaminergic neurons in the substantia nigra and commonly produces bradykinesia, rigidity and resting tremor, although non-motor symptoms are also important. Alzheimer's disease is the most common cause of dementia and involves progressive cognitive impairment associated with characteristic pathological changes including amyloid plaques and tau-related neurofibrillary pathology, although clinical dementia is biologically heterogeneous. Motor neurone diseases affect motor pathways and can produce progressive weakness, while other degenerative disorders affect cerebellar, autonomic, sensory or cognitive systems. Treatment varies substantially and may combine symptom management, disease-modifying therapy where available, rehabilitation, assistive technologies and multidisciplinary support.
Neurology uses imaging, neurophysiology, laboratory testing and sometimes cerebrospinal-fluid analysis to investigate disease. Magnetic resonance imaging provides high-resolution structural information about the brain and spinal cord and is particularly valuable for disorders involving white matter, tumours, vascular lesions, inflammation and structural abnormalities. Computed tomography is widely used in acute neurological assessment because it is rapid and effective for detecting many forms of intracranial haemorrhage and other emergencies.
Electroencephalography measures electrical activity of the brain and is particularly useful in evaluating suspected seizures. Electromyography and nerve-conduction studies assess peripheral nerve and muscle physiology and can help distinguish neuropathy, nerve-root disease, neuromuscular-junction disorders and primary muscle disorders. Lumbar puncture permits analysis of cerebrospinal fluid and can provide evidence of infection, inflammation, bleeding or selected neurodegenerative processes.
Neurological disorders frequently involve complex interactions among genetics, immunity, vascular biology and systemic disease. Multiple sclerosis is an immune-mediated disease of the central nervous system involving inflammatory demyelination and neurodegeneration, commonly producing episodes or progression of neurological dysfunction. Peripheral neuropathy can result from diabetes, nutritional deficiency, toxins, autoimmune disease, inherited disorders, medications or compression.
Migraine is a neurological disorder involving recurrent attacks that may include headache, nausea, sensory sensitivity and neurological aura, and its mechanisms involve altered neuronal and vascular signalling rather than simply abnormal blood-vessel dilation. Autoimmune neurological diseases can target receptors, ion channels, myelin or other components of the nervous system. Neurology therefore requires recognition that neurological symptoms may result from vascular, inflammatory, infectious, neoplastic, degenerative, metabolic, toxic, genetic or structural mechanisms.
