Second edition

01.qxd 3/10/08 9:33 AM Page 12
12 Diagnostic assessment
instructing the patient to bite down. Sensory testing, to
both light touch and pin-prick, is checked in all three divisions,
namely the ophthalmic, maxillary, and mandibular.
The corneal reflex, which tests both the cranial nerves V
and VII, may also be performed by lightly touching a wisp
of cotton to the patient’s cornea, after which there should
be a bilateral blink.
CRANIAL NERVE VII
The facial nerve is first tested for voluntary facial movements
by asking the patient to wrinkle the forehead and
subsequently to show the teeth. In cases of unilateral voluntary
facial paresis note must be made of which divisions
of the facial nerve are involved: the upper (controlling
forehead wrinkling), the lower (controlling elevation of the
side of the mouth), or both. At times facial weakness may
be quite subtle, manifesting perhaps only with a slight flattening
of the nasolabial fold on one side.
After voluntary movements have been tested, the physician
must then test for involuntary or ‘mimetic’ facial
movements. This may be accomplished by telling a joke,
or, if the physician is in less than a humorous mood, by
simply observing the patient for any spontaneous smiling.
Voluntary and involuntary facial movements are quite distinct
neuroanatomically and thus both should be tested for
(Hopf et al. 1992). Voluntary facial palsy affecting only the
lower division indicates a lesion of the pre-central gyrus or
corticobulbar fibers, whereas emotional facial palsy (Section
4.8) indicates a lesion in the supplementary motor area,
temporal lobe, striatum, or pons.
CRANIAL NERVE VIII
The vestibulocochlear nerve is generally tested by gently
rubbing the fingers together about 30 cm from the patient’s
ear and asking whether anything is heard; alternatively,
one may bring a ticking watch in from a distance and ask
the patient to indicate when it is first heard. If there are any
abnormalities, both Weber and Rinne testing should be
performed to determine whether the hearing loss is of the
conduction or sensorineural type.
In the Weber test, a vibrating tuning fork is placed
square on the midline of the patient’s forehead and the
patient is asked whether it sounds the same on both sides
or is heard louder on one side than on the other. In the
Rinne test, a vibrating tuning fork is placed against the styloid
process and the patient is asked to indicate when the
sound vanishes, at which point the tines of the tuning fork
are immediately brought in close approximation to the ear
and the patient is asked whether it can now be heard. With
conductive hearing loss, the Weber lateralizes to the side
with the hearing loss, and on Rinne testing, bone conduction
(i.e., with the tuning fork against the styloid process)
is louder than air conduction (i.e., with the tines of the fork
vibrating in the air just outside the ear). With sensorineuronal
loss, the Weber lateralizes to the ‘good’ side and, on
Rinne testing, air conduction is better than bone conduction
bilaterally.
CRANIAL NERVES IX AND X
The glossopharyngeal and vagus nerves are tested with the
gag reflex and by observation for symmetric elevation of
the palate during phonation.
CRANIAL NERVE XI
The spinal accessory nerve is tested by having patients shrug
their shoulders against the resistance of the physician’s
hand and by turning the head to one side or the other while
the physician exerts contrary pressure on the jaw.
CRANIAL NERVE XII
The hypoglossal nerve is tested first by asking the patient to
open the mouth and then observing the tongue, as it rests
in the oropharynx, for any atrophy or fasciculations. Once
this has been accomplished, the patient is asked to protrude
the tongue as far as possible, noting especially whether it
protrudes past the lips and also whether it deviates to one
side or the other.
Sensory testing
Elementary sensory testing involves light touch, pin-prick,
and vibration. Light touch may be assessed by using a wisp
of cotton, or simply by a light touch with one’s finger, and
pin-prick sensation is tested using a disposable safety pin.
Vibratory sensation is tested by touching a vibrating tuning
fork to a bony structure (such as a finger joint, the lateral
malleolus, or the great toe) and asking the patient
whether he or she can tell if it is vibrating; if so, the tuning
fork is held in place and the patient is asked to say when the
vibration ceases, with the physician taking note, in a rough
sort of way, of how much the tuning fork is still vibrating at
that point. If there are any abnormalities in elementary
sensation it is critical to determine whether or not they
are bilateral. In general, it is sufficient to test sensation
at both hands and both feet, reserving more detailed testing
for cases in which the history suggests a more focal
sensory loss.
Graphesthesia and two-point discrimination tests also
constitute part of the sensory examination but these
should only be used if elementary sensation is intact.
Agraphesthesia is said to be present when patients, with
their eyes closed, are unable to identify letters or numerals
traced on their palms by a pencil or dull pin. Two-point
discrimination may be tested by ‘bending a paperclip to
different distances between its two points . . . [starting]
with the points relatively far apart . . . [then] approximated
until the patient begins to make errors’ (Dejong 1979). As
two-point discriminatory ability varies on different parts