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Neurological Assessment and Monitoring 431

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speaking, performing calculations). Such activity is goal- exceptions, act on their effectors by releasing the neu-
directed and largely learned, and improves with practice. rotransmitter adrenaline and the related compound nor-
In rhythmic motor patterns, the initiation and termina- adrenaline. This system is therefore described as adrenergic,
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tion may be voluntary, but the rhythmic activity itself which means ‘activated by adrenaline’. The autonomic
does not require conscious participation (e.g. chewing, regulation of several organ systems of particular impor-
walking, running). Reflex responses are simple, stereo- tance in clinical practice is illustrated in Figure 16.12. 15
typed responses that do not involve voluntary control
(e.g. deep tendon reflexes or withdrawal of a limb from NEUROLOGICAL ASSESSMENT
a hot surface). Motor control is carried out in a hierarchi- AND MONITORING
cal yet parallel fashion in the cerebral cortex, the brain-
stem and the spinal cord. Modulating influences are This section explores the complex issues surrounding
provided by the basal ganglia and cerebellum through the cerebral haemodynamics and assessment. The objective
thalamus. 1 of assessment is to determine the extent of neurological
injury, recognise fluctuations in condition and imminent
Sensory Control deterioration, and assist in maintaining cerebral perfu-
The somatic sensory system has two major components: sion as part of multimodal monitoring.
a subsystem for the detection of mechanical stimuli (e.g. PHYSICAL EXAMINATION
light touch, vibration, pressure, cutaneous tension), and
a subsystem for the detection of painful stimuli and tem- The neurological physical exam begins at the onset of
perature. Together, these subsystems give the ability to patient contact, and the priorities are defined by a primary
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identify the shapes and textures of objects, to monitor the survey and vital signs. The history and contact with family
internal and external forces acting on the body at any can inform the clinical exam and should include the
moment, and to detect potentially harmful circumstances. patient’s normal baseline status, medications and other
Mechanosensory processing of external stimuli is initi- substance use, and past neurological symptoms such as
ated by the activation of a diverse population of cutane- syncope or seizures.
ous and subcutaneous mechanoreceptors at the body Specific areas tested during the initial physical exam
surface that relays information to the central nervous include level of consciousness, general behaviour,
system for interpretation and ultimately for action. Addi- memory, attention and concentration, abstract thought
tional receptors located in muscles, joints and other deep and judgement. Not every aspect of the examination will
structures monitor mechanical forces generated by the be relevant in all critical care situations and therefore may
musculoskeletal system, and are called proprioceptors. not be tested. Nevertheless, the clinician should under-
Mechanosensory information is carried to the brain by stand how all components are integrated and how they
several ascending pathways that run in parallel through influence priority decision making for patient care. At
the spinal cord, brainstem and thalamus to reach the change of shift, performing a physical exam with the
primary somatic sensory cortex in the postcentral gyrus incoming nurse ensures clear communication of the
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of the parietal lobe. The primary somatic sensory cortex patient’s previous status. The patient’s ability to perform
projects in turn to higher-order association cortices in the should be taken into consideration, as it may be neces-
parietal lobe, and back to the subcortical structures sary to modify assessment techniques. For example, intu-
involved in mechanosensory information processing. bated patients who are otherwise awake and aware may
Autonomic Nervous System gesture or write answers to questions instead of verbalis-
ing them. In addition, when patients are the recipients of
The autonomic nervous system, with its three major divi- very frequent neurological assessment over an extended
sions (sympathetic, parasympathetic and enteric), is period of time (including arousal and awareness, pupil
largely an involuntary system and is part of the efferent and motor response) sleep and sensory rest deprivation
division, as we saw in Figure 16.1. It allows the body to is common. Sleep deprivation and sensory overload will
adjust to rapidly changing external events (the ‘flight or confound assessment accuracy. Therefore careful consid-
fight’ response of the sympathetic division), and to regu- eration needs to be given in regard to the priorities of
late internal activities (blood pressure, temperature, assessment and rest; a plan needs to implemented to
airway and breathing, urinary function, digestion by the promote rest as neurological injury requires rest and sleep
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parasympathetic and enteric divisions). Whereas the for restoration. See Online resources for links to a full neu-
major controlling centres for somatic motor activity are rological assessment and physical examination protocol.
the primary and secondary motor cortices in the frontal
lobes and a variety of related brainstem nuclei, the major Conscious State
locus of central control in the visceral motor system is the Arousal and awareness are the fundamental constituents
hypothalamus and the complex circuitry that it controls of consciousness and should be evaluated and docu-
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in the brainstem tegmentum and spinal cord. The status mented repeatedly for trend analysis. Changes in the con-
of both divisions of the visceral motor system is modu- scious state are the first to change in deterioration.
lated by descending pathways from these centres to pre-
ganglionic neurons in the brainstem and spinal cord, Arousal assessment
which in turn determine the activity of the primary vis- The evaluation of arousal focuses on the ability to be
ceral motor neurons in autonomic ganglia. The post- able to respond to a variety of stimuli and can be
ganglionic neurons of the sympathetic system, with few described using the AVPU scale or terms such as