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Neurological observations 1

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William T. Blows, PhD, BSc, RGN, RNT, OStJ.

Lecturer in biological sciences, St Bartholomew School of Nursing and Midwifery, City University, London.

What are neurological observations?

Neurological observations are the examination of the patients nervous system to assess the responses to various stimuli. This provides information about nervous system function.

Why are they done?

Accurate interpretation of neurological observations can give important indications as to what changes may be occurring within the brain, and help to determine when urgent intervention is needed or what progress the patient is making. The main assessments are made on the eyes and on consciousness.

How are the eyes tested and interpreted?

Pupils 

  • The normal pupil is round with a size range from 2-6mm in diameter, averaging about 3.5mm in diameter (Fig 1a).
  • Shining a bright light into the corner of one eye normally causes a rapid constriction of both pupils.
  • The pupil receiving the light shows a direct reaction, the opposite pupil shows a consensual reaction.
  • This is activated by a reflex arc through two cranial nerves (II and III) and the brain stem.
  • It is a means of testing both brain stem and cranial nerve function.
  • Nurses observe to see that both the pupils are equal in size (right with left) and that they both respond rapidly to light.
  • Pinpoint (miotic) pupils, i.e. up to 1mm in diameter, may be caused by obstruction of the sympathetic supply to the eye or as a result of opiate drug use.
  • Miotic drugs such as pilocarpine are used in the treatment of glaucoma to create small or pinpoint pupils.
  • Dilated pupils (mydriasis), i.e. up to 6-8mm diameter, are a normal response to low light, or as a result of amphetamine drug use.
  • Mydriatic or cycloplegicdrugs (for example, tropicamide, cyclopentolate and homatropine) dilate the pupil for eye examination purposes.
  • Pupil observations are important to identify raised intracranial pressure (RICP) caused by a space-occupying lesion (SOL) such as intracranial bleeding, cerebral oedema or tumour.
  • A unilateral, ipsilateral (on the same side as the lesion), fixed dilated pupil is the initial focal sign, followed by bilateralfixed dilated pupils, occurring anything from minutes to hours later.
  • A fast or slowly developing SOL causes pressure on the brain stem areas that control pupil constriction or on the oculomotor nerve (cranial nerve III).
  • Compression would displace the brain stem and cause the centres for cardiac and respiratory control to fail.

Gaze 

  • Following the examiners finger through up, down, left and right movements may demonstrate abnormal gaze shifts.
  • Abnormal gaze holding occurs in patients with paralysis of one of the cranial nerves controlling eye muscles, and the two eyes no longer function together.
  • Nystagmus is the involuntary rapid back and forth movement of the eye in a horizontal or vertical plane. It may be caused by cerebellar, brain stem or vestibular diseases.

Papilloedema 

  • Papilloedema is oedematous swelling of the optic disc, seen through an ophthalmoscope (Fig 2).
  • The optic disc is just off centre from the macula, on the retina of the eye.
  • In papilloedema, the normal visible disc margin becomes obscured, red and distorted
  • Raised intracranial pressure (RICP) is the main cause of papilloedema, since the high pressure involves the meninges that extend to the optic disc.
  • It is also done before a lumbar puncture (LP) to identify any RICP present.

Consciousness

Awareness is the appreciation of environmental stimuli, and the conscious thought that results. There are various degrees of consciousness, forming a spectrum from fully conscious to a deep unconsciousness (or coma). Points along this spectrum are the altered states of consciousness.

How is consciousness tested and interpreted? 

  • Assessing the level of consciousness (Table 1) identifies the point the patient is occupying on the consciousness spectrum, and may highlight if the patient is regaining or loosing consciousness.
  • The nurse carries out a sensory stimulus and observes the patients response.
  • The coma scale records the patients best response to that stimulus.
  • The nurse asks the patient a simple question. If there is no response this is followed by a louder sound, such as a command or a hand clap.
  • Tactile stimuli are tried if there is no response to sound, e.g. gently shaking their arm. Tactile stimuli can be increased from touch to pain if necessary.
  • Pain is a powerful stimulus of the cerebral cortex, but its application must be in a manner that causes no injury to the patient. Pressure applied to the finger or toe nails will not cause tissue injury.
  • Pain causes a verbal or non-verbal motor response.
  • Purposeful responses are those where a limb moves specifically to remove the pain. Non-purposeful responses are limb movements that are obviously not related to pain avoidance.
  • No response at all to pain indicates the patient is in a deep coma.
  • Purposeful withdrawal from pain suggests a light coma, with brain stem reflexes intact.
  • Non-purposeful responses to pain indicate a medium coma with variable brain stem reflex responses.
  • Unresponsive to pain is a deep coma, with absent brain stem reflexes.
  • The Glasgow Coma Scale measures eye opening responses, motor responses to both verbal commands and painful stimuli and the ability to speak.

Table 1. Levels of consciousness (Blows, 2001)

 

Terminology

 

 

Definition

 

 

Fully conscious

 

 

Awake and alert

 

 

Confusion

 

 

disorientated in time, place and person

 

 

Lethargy

 

 

orientated but very slow in motor activity and speech

 

 

Obtundation

 

 

very drowsy; arousable only when stimulated; limited verbal responses

 

 

Stupor

 

 

generally unresponsive except to pain and vigorous verbal or touch stimuli

 

 

Coma

 

 

Unresponsive even to pain

 

Raised Intracranial pressure 

  • Raised intracranial pressure (RICP) is a sustained pressure within the skull over 20mmHg, with general or local (focal) symptoms.
  • General symptoms identify the presence of pressure on the brain. They include headache (worse on wakening), nausea, vomiting, bradycardia, raised blood pressure, nystagmus, visual field defects, fits, altered state of consciousness, blurred vision, respiratory irregularities and papilloedema.
  • Local (focal) symptoms indicate the site of pressure on the brain. Focalsymptoms are unilateral, ipsilateral fixed dilated pupil followed by bilateral fixed dilatedpupils,aphasia, ataxia, hemiperesis, hemiplegia and specific sensory losses.
  • Compensatory mechanisms allow for some increase in the size of the SOL without gross changes in the intracranial pressure (ICP). These compensations fail eventually and the ICP will rise sharply. This is the critical point, the change from compensation to decompensation, causing rapid deteriorate if nothing is done.

Further reading

Downey, D., Leigh, R. (1998) Eye movements: pathophysiology, examination and clinical importance. Journal of NeuroscienceNursing; 30: 1, 15-24.

Richards, D. et al (eds) (2007) The Human Brain and its Disorders. Oxford: Oxford University Press.

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