Examination Of The Nervous System - pediagenosis
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Thursday, August 22, 2019

Examination Of The Nervous System

Examination Of The Nervous System
The examination of the nervous system can be broken down into a number of separate assessments.

Cognitive examination
There are a number of widely available assessment tools including the Mini Mental State Examination (MMSE; <25 is taken to indicate dementia) and the revised Addenbrooke’s Cognitive Examination (ACE-r). However in clinic, targeted tests of cognition are very helpful at delineating the main site of pathology causing cognitive problems. However, these tests are only useful to do if the patient has a normal level of consciousness, is able to pay attention and has no major problem with language.

Examination Of The Nervous System, Frontal lobe function, Parietal lobe function, Temporal lobe function, Cranial nerves, Motor system examination of the limbs, Sensory examination,

·      Orientation in time, person and place: if these cannot be correctly answered (assuming the patient has no major language deficits) then the patient is either acutely confused or severely demented, in which case the remainder of the cognitive examination is unlikely to be helpful.

Frontal lobe function
·   Verbal fluency: number of words generated beginning with a certain letter (e.g. ‘s’) or specific category (e.g. animals) over a 60- or 90-second period.
·       Concentration: the ability to take in and repeat back immediately a list of objects or a name and address.
·   Primitive reflexes: including pouting of the lips when they are tapped and grasping the examiner’s hand when it is gently moved across the patient’s hand.

Parietal lobe function
·  Attention: or neglect of visual or somatosensory stimuli in the contralateral sensory hemifield.
·    Dyspraxia: the patient is unable to form, copy or mime gestures and common tasks (e.g. combing hair).
·       Visuospatial function: the ability to copy drawings (e.g. interlocking pentagons).

Temporal lobe function
·   Anterograde memory: the ability to remember a standard name and address given to the patient (e.g. Peter Marshall, 42 Market Street, Chelmsford, Essex) 5 minutes after it has been given. It is though important to ensure that the patient has taken in information in the first place.
·   Language: language assessment involves listening to spontaneous speech for content and fluency, naming objects, repeating phrases (e.g. ‘no ifs, ands or buts’), following commands, reading and writing (see also Chapter 28).

Cranial nerves
·     Olfactory nerve: each nostril is tested separately with a range of standard odours.
·    Optic nerve: visual acuity for each eye is tested using standard eyesight charts. The visual fields for each eye are then tested with examination of the blind spot if necessary (see Chapter 24). The fundi (back of the eye) are examined with an ophthalmoscope looking for abnormalities of the retina and optic disc, e.g. swollen (papilloedema) or pale and atrophic (optic atrophy). Colour vision (using the Ishihara colour plates) and pupillary responses can also be tested.
·   Oculomotor, trochlear and abducens nerves: ptosis, pupillary abnormalities and eye movements are looked at (e.g. see Chapters 3, 25 and 56).
·    Trigeminal nerve: sensation is tested in all three divisions of the trigeminal nerve and the power of the jaw muscles. In some cases, the corneal reflex is tested by lightly touching the cornea with cotton wool.
·   Facial nerve: the power of facial muscles is tested, e.g. the patient screws up their eyes tightly, blows out their cheeks or purses their lips. The examiner should not be able to overcome any of these movements.
·    Vestibulocochlear nerve: hearing is tested in each ear by gently whispering a number into each. More formal testing can be per- formed with tuning forks.
·   Glossopharyngeal and vagus nerves: the patient opens their mouth wide and says ‘ahhhhhh’ so that the movement of the palate can be assessed. The gag reflex can be tested by gently placing a spatula against the posterior pharyngeal wall and noting any reflex movement of the palate. Testing the strength and character of a cough can also be helpful in some cases.
·     Spinal accessory nerve: this is tested by getting the patient to turn their head to the right and left and shrug their shoulders. The examiner should not be able to overcome this movement.
   Hypoglossal nerve: this is tested by looking at the tongue in the floor of the mouth for wasting or fasciculation; it is then protruded from the mouth and any deviation from the midline noted. Power is tested by getting the patient to push the tongue into each cheek, assuming they do not have any significant facial weakness.

Motor system examination of the limbs
The examination of the motor system includes:
     Observation: involuntary movements, wasting, weakness, fasciculation, scars or deformities.
     Tone: the limb is gently moved and its stiffness assessed. Stiffness is increased in Parkinson’s disease or upper motor neurone (UMN) lesions and decreased in lower motor neurone (LMN) or cerebellar lesions (see Chapters 35–42). Sometimes the tone is increased because the patient cannot relax or is in pain.
    Power: movements are assessed and scored according to the Medical Research Council (MRC) rating scale (see figure).
      Coordination: the ability to coordinate movements in the upper limb is tested by getting the patient to touch the examiner’s finger and then their own nose with the same finger after it has slowly moved about in front of the patient. This may be abnormal if there is weakness, sensory loss or cerebellar disease. In the lower limb, coordination is tested by getting the patient to walk normally, then heel–toe walking and finally by getting the patient to run their right/ left heel along their left/right shin, respectively, while lying down.
       Reflexes: these are tested by tapping the tendons at certain sites in the upper and lower limb. Reflexes can be absent, reduced, normal or brisk. The latter implies a UMN lesion while reduced or absent reflexes implies a dysfunction in part of the spinal mono- synaptic reflex (see Chapter 35).
     Plantar responses: the sole of the foot is gently scratched along its lateral aspect and the toes should fan out and the big toe go down (flexor or normal plantar response). If the toes point up and this is not a withdrawal response, it implies a UMN lesion.

Sensory examination
Sensation in the limbs is tested at the extremities and in the dermatomes using a number of tests.
     Light touch: cotton wool is gently applied to the skin, having checked that the patient can feel it normally (test on face first, assuming there is no trigeminal sensory loss).
       Pinprick: a blunted pin is used.
       Temperature: cold and hot tubes or objects are used.
     Vibration perception threshold (VPT): a tuning fork is applied to the distal interphalangeal joint or big toe. The patient must feel it vibrating, not just feel it being applied to the joint. If it is not felt to vibrate, the fork is moved proximally.
       Joint position sense (JPS): this is tested by slightly moving the terminal joint in the hand or toe, having checked that the patient understands what is meant by up and down movements. This movement should be very slight, as JPS is very sensitive in humans. If the movement cannot be detected then larger movements are made at these joints before moving to more proximal joints, in the same way as for VPT.

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