Assessment of extraocular functions
The examination begins with visual inspection. The patient is asked to fixate their gaze on the physician's finger or a neurological hammer held directly in front of them. The physician evaluates the symmetry and width of the palpebral fissures, the presence of ptosis (drooping of the eyelid), and checks for potential retraction (enophthalmos) or protrusion (exophthalmos) of the eyeballs. The size and shape of the pupils are routinely recorded.
Next, the range of eye movements is tested. The patient is asked to follow an object upward, downward, inward, and outward.
Specific signs of lesions:
- When upward, inward, and partial downward movements are restricted, divergent strabismus (strabismus divergens), mild exophthalmos, pupillary dilation (mydriasis), and ptosis may be observed. Pupillary light reflexes, accommodation, and convergence are also impaired.
- If the patient looks downward and complains of double vision (diplopia), while the eye is slightly turned upward and inward (strabismus convergens), this indicates an isolated restriction of downward gaze.
- Inability to abduct the eye outward is accompanied by convergent strabismus (strabismus convergens). When attempting to look toward the side of the lesion, diplopia increases significantly.
Examination of facial muscles
To assess facial muscle function, the face is conventionally divided into upper and lower parts.
Upper muscle group: the patient is asked to raise their eyebrows (forehead creases should be symmetrical), frown (eyebrows should move uniformly toward the midline), and close their eyes tightly.
Lower muscle group: the patient is asked to show their teeth, smile, puff out their cheeks, and try to blow out an imaginary match (while pursing the lips into a pout).
Differential diagnosis of palsies:
- Peripheral palsy: the entire half of the face is affected. The eye on the affected side does not close (lagophthalmos). Forehead creases are smoothed out, and frowning is impossible. Bell's sign is characteristic: when attempting to close the eyes tightly, the eyeball shifts upward, and the iris hides beneath the upper eyelid while the palpebral fissure remains gapping. The corner of the mouth is drooped, liquid food spills out, and speech is impaired. When attempting to show the teeth, the mouth skews toward the healthy side.
- Central palsy: only the lower part of the face on the side contralateral to the lesion is affected. Forehead creases and eyelid closure are preserved, but the corner of the mouth is drooped, and facial asymmetry with deviation toward the healthy side is observed when showing the teeth.
Assessment of bulbar functions and the tongue
Bulbar functions are assessed by examining the soft palate, voice, and swallowing. The patient is asked to open the mouth and say "ah". Normally, the palate tightens symmetrically, and the uvula lies strictly in the midline. Next, the vocal timbre during speech is evaluated, and the patient is asked to take a few sips of water.
Signs of bulbar impairment:
- The soft palate on the affected side sags and contracts poorly during phonation.
- The uvula deviates toward the healthy side.
- The voice acquires a characteristic nasal, hypernasal tone.
- Palatal and pharyngeal reflexes are lost.
- Dysphagia (swallowing disorder) develops.
The tongue is evaluated separately. When protruded from the mouth, it normally lies in the midline. In pathology, deviation (to the side of the lesion) is observed. In peripheral palsy, muscle fiber atrophy develops on the affected half. The patient's speech becomes indistinct and slurred (dysarthria).
Checking pupillary reactions
Testing pupillary reflexes is a crucial step in the neurological examination.
- Direct light reflex: the physician alternately covers the patient's eyes with their palms and then quickly uncovers them. Normally, the pupil should constrict instantly.
- Consensual reflex: one eye is covered, then uncovered while observing the reaction of the other (fellow) pupil. It should also constrict.
- Convergence reaction: the patient fixes their gaze on an object that the physician moves closer to and farther from the face. Maximal pupillary constriction normally occurs at a distance of 10–15 cm, and they dilate when moved away.
- Accommodation reaction: tested for each eye separately. When focusing on a near object, the pupil constricts; when shifting gaze to a distance, it dilates.
Briefly: answers to topical questions
Which cranial nerves are responsible for bulbar functions?
Bulbar impairments in the literature are associated with the IX, X, and XII cranial nerve pairs.
- IX and X pairs (glossopharyngeal and vagus nerves) — paralysis of the motor component innervating the striated muscles of the soft palate, pharynx, and larynx; manifestations: choking, dysphagia, phonation disorders (hypernasality, aphonia).
- XII pair (hypoglossal nerve, n. hypoglossus) — lesions result in bilateral paralysis, dysarthria, and complete immobility of the tongue.
Which cranial nerves innervate the extraocular muscles?
Extraocular muscles are innervated by the III, IV, and VI cranial nerve pairs.
- Oculomotor nerve (n. oculomotorius, III pair) — innervates the intraocular muscles, rectus muscles (except the lateral one), and the inferior oblique muscle.
- Trochlear nerve (n. trochlearis, IV pair) — innervates the superior oblique muscle (outward and downward movement).
- Abducens nerve (n. abducens, VI pair) — innervates the abductor (lateral rectus) muscle.
In which acute intestinal infection is the combination of bulbar and extraocular syndromes most common?
The combination of extraocular (ophthalmoplegic) and bulbar syndromes is characteristic of botulism.
In the advanced stage of botulism with nervous system involvement, ophthalmoplegic and bulbar syndromes are noted, along with impaired external respiration. Extraocular disorders are associated with damage to the III, IV, and VI cranial nerves, while bulbar disorders involve the IX, X, and XII pairs.
Class and exam questions
What is the main difference between central and peripheral facial muscle palsy?
In central palsy, only the lower facial muscles are affected, while the ability to frown the forehead and close the eye is preserved. In peripheral palsy, the entire half of the face is affected, including the upper facial muscles.
What is Bell's sign?
This is a pathological sign where, upon attempting to close the eye, the eyeball reflexively rolls upward while the palpebral fissure remains open (lagophthalmos).
How does the voice change in lesions of the nerves innervating the soft palate?
The voice loses its resonance and acquires a nasal, hypernasal tone due to sagging of the soft palate.
What else to study on this topic
- Anatomy and functions of the oculomotor, trochlear, and abducens nerves
- Differential diagnosis of bulbar and pseudobulbar syndromes
- Mechanisms of direct and consensual pupillary light reflexes
- Causes of diplopia in isolated cranial nerve lesions
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