Examination of Cranial nerves I to VI: Simple language and Video

Clinical Examination of Cranial Nerve I- VI(Part I) 

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I Olfactory Nerve: Sense of smell

Items needed for Olfactory Nerve Test 1.     Clove  2.     Coffee  3.     Soap

Commonly encountered objects can be used to make the patient smell the object and ask them about the smell of the object with each nostril closed individually and both eye closed.

Pungent smell producing substances such as onion and all are contraindicated because it can as well stimulate the trigeminal nerve to alter the interpretation.

Want to know what causes altered sensation of smell?

II Optic Nerve 

Items needed for Optic Nerve Test 1.     Pen 2.     Pen Torch 3.     Snellens chart 4.     Ischihara Chart/ Three thumbpin of color RBY 5.     White thumb pin

. In the examination of Optic Nerve, we perform the test to evaluate the following functions of optic nerve.Ophthalmoscopic examination for retina may not be feasible and come within the scope of this text.

Visual Acquity: It is evaluated using initially hand movement, finger counting and Snellens Chart which is kept at a distance of 6m from the patient and asked to identify the character in the chart with  one eyes closed at a time.

Visual Field: Visual Field is grossly evaluated using the confrontation test, where the eyes of both patient and examiner placed 1 m apart are closed on the same side. (Right for patient and left for the doctor and vice versa) and a moving finger or a pin with white colored head is brought towards the centre from the periphery. The patient is asked to tell the examiner whenever he sees the object. The finding is compared with the vision of examiner (Considering examiner as normal visual field).

Color vision: Ischihara Chart is the perfect tool to measure the color vision. In absence of that any three thumb pins with red, blue and yellow colors (Primary colors) can be used to evaluate the color vision.

Light reflex: The light is shown into the pupil being brought from the periphery and the constriction of ipsilateral pupil (Direct) and contralateral pupil (Indirect) is evaluated. A hand must be kept in between the two eyes to make sure that the light does not strike the contralateral pupil to stimulate its direct  light reflex. We need a torch light with white light to perform the light reflex. Swinging light reflex can be performed to look for RAPD (Rapid Afferent Pupillary Defect).

Know how pupils reacts to various substances, drugs and physiological condition.

Accommodation reflex and Convergence: A pointed object especially a pen or pencil is kept beyond the distance of 25cm and the patient is asked to focus upon its tip. The pen is brought towards the glabella and the accomodation reflex of convergence and miosis can be noted clinically. The afferent pathway for accommodation reflex is optic nerve and efferent is occulomotor nerve. So it tests both the nerve.

III/IV/VI: Oculomotor, trochlear, Adbucens nerve.
Accomodation reflex also forms the part of III IV VI Cranial Nerve examination.

Items needed for Extraocular muscle Examination 

1.     Pen

A pen or a sharp tip object is taken and the patient is asked to focus on the tip and follow the pointed end without turning their head. The object is moved in a fashion to make a large shape of H within his visual field and the movement of the eye is evaluated for monoocular and binocular vision.

V: Trigeminal Nerve

Items needed for Trigeminal Nerve Test 1.     Cotton 2.     Pin / Tooth pick 3.     Reflex Hammer The trigeminal nerve is evaluated for both its motor and sensory function. Must Have instruments needed to perform CNS examination.

The motor branch innervates the muscle of mastication and temporalis muscle. The strength of trigeminal nerve is evaluated by asking the patient to clench his teeth and the volume and tone of muscles evaluated by palpating the strength of masseter and temporalis.

On asking the patient to open the mouth, the chin will be deviated towards the paralysed side. Similarly asking the patient to move the mandible against the resistance of hand, the paralysed side will not move laterally.

Jaw jerk is a muscle stretch reflex carried out by keeping the mouth partially open and index finger of the examiner placed over the jaw. A reflex hammer is used to tap the finger placed over the mandible directed downward.

Sensation of the trigeminal nerve is grossly evaluated over the ophthalmic, mandibular and maxillary division. With the eyes closed, the patient is asked to describe whether one or both side of their face is touched and if they are different. Use a cotton or the pulp of the finger to evaluate the fine touch. Similarly use a tip of blunted pin or tooth pick to evaluate pin prick.

Corneal reflex and conjunctiva reflex both have a afferent pathway carried by the trigeminal nerve and efferent pathway by the facial nerve. So, the patient must be described what is being done and a twisted end of cotton is brought to the limbus or conjunctiva respectively from the lateral canthus and touched softly. A brisk reflex presents with blinking of eyelid instantaneously and bilaterally.

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