The latency refers to the time between the presentation of a stimulus and the motor, sensory, autonomic, or behavioural response of the patient. This provides information concerning conduction time along nerve axons and spatial and temporal summation occurring in the neurons involved in the functional action chain of the response. The velocity of the response is another window of spatial and temporal summation and conduction time.

The time to summation (TTS) and time to peak summation (TTSp) are terms that describe, respectively, the latency and average velocity of effector responses. The pupillary action observed in response to a light stimulus offers a good illustration of these concepts. Under normal conditions, the pupils will respond with a relatively equal TTS and TTSp in both eyes when stimulated with an equal light stimulus. However, in the situation where the central integrative state of the neurons in the right Edinger–Westphal nucleus or mesencephalic reticular formation is further away from threshold, the TTS of the right eye would be expected to be increased from that of the left. The same result may be expected when measuring the velocity of the response, or an increased time to maximal pupil constriction (increased TTSp). The same result, that is increased TTS and TTSp in the right eye, may be found with an afferent pupil defect such as would occur if the right eye end organ was impeded by a photoreceptor or axonal conduction deficit such as in retinal or optic nerve dysfunction. Thus there is the need for a complete fundoscopic and visual acuity examination when unequal pupil responses are present.

The amplitude of the response refers to the maximum change in the parameters being assessed. This can be a useful indicator of the relative frequency of firing in a neuronal pool: for example, the degree of excursion of the eye during the smooth phase of pursuit movement during optokinetic testing of eye movements; or, in keeping with our first example, the maximum change in pupil size when testing the pupil light reflex.

Smoothness of any movement is dependent on complex interactions between multiple neuronal pools. An example is the smoothness of visual tracking in the horizontal plane. This requires complex interactions between the cerebellum, vestibular system, neural integrator, and occipital, parietal, and frontal lobes. A poor central integrative state in any of these areas may affect the quality of visual tracking in one or more directions. Specific features of the visual tracking deficit may alert to greater involvement of one area over another. Uncoordinated or jerky movements are referred to as dysmetric.

This refers to the ability to maintain a response during continued or repeated presentation of a stimulus. A progressive reduction in ocular roll and skew deviation between successive head tilts is an example of increasing fatigue of the ocular tilt reaction (OTR). Poor maintenance of a response reflects increased fatigability. The fatigability coefficient is an arbitrary descriptor of the fatigability of a neuronal pool.

The direction of response elicited is compared to the expected normal response to provide further information about the integrity of a neuronal pool. For example, the direction of change of pupil size when shining a light in the eye, the direction of nystagmus during caloric irrigation of the ear, and the direction of change of skin temperature in response to a cognitive task or vestibular stimulation all have an expected normal response direction. If the direction of response is different from the expected outcome, this may indicate the presence of pathology, fatigue, or plastic alterations in neural circuitry.

Any healthcare practitioner with training in clinical and neural science has the ability to perform the neurological history and examination in a proficient manner. The key is to develop a routine that can easily be remembered, that can be performed in logical sequential order, and that can be easily improvised for different patient presentations. Two systematic approaches to the neurological examination include the anatomical and functional approaches. The anatomical approach requires examination of the nervous system in a rostrocaudal order (i.e. brain, brainstem/cranial nerves, spinal cord, spinal nerves, receptors, etc.), while the functional approach requires examination of related functions in groups (i.e. mental, motor, sensory, visceral, etc.). A combination of these two approaches is likely to be more efficient, less repetitive, and more appropriate for both the history-taking process and examination as well.

Greater efficiency may be achieved by limiting movement of the patient and using each tool or each type of test only once throughout the examination. If possible, the patient should be assessed in the sitting, standing, and lying positions once and should be assessed in a rostrocaudal order for each function tested. This will reduce the frequency of switching between tools and patient positions. Each instrument used in the examination should be laid out in order of use and within easy reach of the practitioner. With this orderly approach, the practitioner will be less likely to miss any component of the examination (DeMyer 1994). For example, it might be more efficient for the practitioner to determine sensitivity to pain at all levels from the ophthalmic division of the trigeminal nerve to sacral innervated regions, rather than switching between motor and sensory tests at each level.

Details gathered from the neurological history and examination may only provide information concerning the type and location of aberrant neuronal function. A thorough physical and orthopaedic examination and laboratory or ancillary neurodiagnostic tests may be more useful in establishing the aetiology in some cases.

The following lists provide an overview of the breadth of information concerning the neurological history and examination. This should serve as a useful reference and template.

3. Social History

4. Systems History (special senses, motor, sensory, autonomic, mental)

A variety of neurodiagnostic testing equipment can be utilised to investigate or objectively quantify dysfunction. These include:

Accommodation is the constriction of the pupil that occurs during convergence of the eyes for close focusing. The Edinger–Westphal nucleus is activated by the adjacent oculomotor nucleus, which activates the medial rectus muscle more powerfully than the light reflex. There is also contraction of the ciliary muscle to aid close focusing, which is referred to as the ‘near response’. Parasympathetic fibres lie superficially on the oculomotor nerve and they relay in the ciliary ganglion of the orbit, which lies on the branch to the inferior oblique muscle. They begin in dorsal position and rotate to a medial and then inferior position as they enter the orbit. Blood supply to the pupil fibres is different from the main trunk of the nerve. The pupil fibres receive their blood supply from the overlying pia mater; therefore, the pupil fibres are usually spared in an oculomotor nerve trunk infarction.

An ‘afferent pathway lesion’ results in a Marcus-Gunn pupil