The eyelids protect the eye and help maintain the corneal tear film. Ptosis (drooping), retraction (abnormal elevation), facial weakness (causing insufficient eyelid closure), abnormal blinking (absent or excessive), and other abnormal eyelid and facial movements are the most important eyelid and facial nerve disorders in neuro-ophthalmology. This chapter reviews the relevant neuroanatomy, examination of the eyelids and facial nerve, and differential diagnosis of these and other eyelid abnormalities. At the end of the chapter, diseases that are commonly associated with ptosis or facial weakness are discussed.
Neuroanatomy
Eyelids
Upper eyelid muscles and their innervations . The levator palpebrae superioris muscle, with minor contributions from Müller’s (superior tarsal) muscle and the frontalis muscles, maintains the normal position of the upper eyelid. The aponeurosis of the levator muscle attaches to the anterior surface and the superior edge of the superior tarsal plate ( Fig. 14.1A ). Both levator muscles are controlled by the central caudal nucleus (CCN) of the oculomotor nuclear complex (cranial nerve III) (see Chapter 15 ). Within the CCN, which is a single midline subnucleus, neurons to both levators are intermixed. Müller’s muscle is innervated by oculosympathetic neurons (see Chapter 13 ), whereas the frontalis receives fibers from the facial nerve (see later discussion). Eyelid position depends mainly on the resting tone of the levator muscles, which varies according to the patient’s state of arousal, with individuals having wider palpebral fissures when they are alert than when they are drowsy. Experimental lesions of the frontal lobes, angular gyrus, and temporal lobes may produce ptosis, and experimental stimulation of areas within frontal, temporal, and occipital lobes may produce eyelid opening, but the exact nature of the cortical control of the eyelids is unclear. There is some evidence to suggest that the right hemisphere may be dominant for this function (see Cerebral (or Cortical) Ptosis).
Lower eyelid muscles and their innervations . The inferior tarsal muscle ( Fig. 14.1B ), similar to the superior tarsal muscle in the upper lid, is innervated by oculosympathetic neurons (see Chapter 13 ).
Coordination with vertical eye movements . With only some minor differences in speed and conjugacy, the eyelids move with the eyes during both slow and rapid vertical eye movements. The major nonpathologic exception to this occurs while the eyelids blink, at which time the levator is temporarily inhibited and the orbicularis oculi contracts. Recent evidence suggests that vertical eye movements and lid position are coordinated through the M-group (supraoculomotor area or supra III) in the midbrain ( Fig. 14.2 ). In upgaze, M-group neurons excite the CCN, causing the levator muscles to contract and the eyelids to open. During downgaze, neurons from the interstitial nucleus of Cajal (inC) inhibit the M-group neurons and the CCN, resulting in levator relaxation and eyelid lowering. The nuclei of the posterior commissure (nPC), which lie dorsolaterally to the IIIrd nerve nuclei, may also be important in control of lid–eye coordination. Interconnecting neurons between the nPC on each side travel through the posterior commissure in the dorsal midbrain. More details regarding the anatomy of the IIIrd nerve are discussed in Chapter 15 .
Facial Nerve
Supranuclear pathways . The supranuclear neurons destined to innervate the facial nerve nucleus lie in the precentral gyrus of the frontal lobe ( Fig. 14.3 ). Discharges from this region initiate voluntary movements to command such as smiling or puckering of the lips. Somatotopically, these supranuclear neurons are located most laterally in the frontal cortex just below the representation for the hand. One functional imaging study demonstrated activation of the right primary motor cortex and supplementary motor area during voluntary blinking.
Leaving the precentral gyrus, the axons of the facial motor area coalesce and become part of the corticobulbar tracts that descend through the middle of the internal capsule on their way to the medial part of the cerebral peduncle. In the majority of individuals, at the level of the facial nerve nucleus in the pons, most of the supranuclear fibers cross over to the opposite side to innervate the facial nucleus. However, in some individuals, the supranuclear fibers descend into the ventral medulla before looping rostrally, then crossing to innervate the contralateral facial nucleus. In either case, other corticobulbar fibers mediating ipsilateral upper facial function synapse on the ipsilateral facial nerve nucleus, providing the upper face with innervation from both cerebral hemispheres. This unusual anatomic feature explains classically why supranuclear lesions involving the descending motor pathways result in weakness of the contralateral lower face only ( Fig. 14.3 ), although some have questioned this concept based on evidence that the sparing of the upper face is not absolute in cortical infarctions.
Nuclear and infranuclear . The motor nucleus of the facial nerve resides in the lateral midpons. Motor axons leaving the facial nucleus course dorsomedially toward the fourth ventricle to loop around the VIth nerve nucleus, thus forming the facial colliculus. After bending around the VIth nerve nucleus the motor fibers extend laterally to exit the pons ( Fig. 14.4 ; see also Fig. 15.6 ). The parasympathetic component of the facial nerve originates from the superior salvatory nucleus, which lies just superior to the facial motor nucleus. This nucleus supplies the sublingual, submandibular, and lacrimal glands and forms one part of the nervus intermedius ( Fig. 14.5 ). The other component of the nervus intermedius is sensory, containing those fibers subserving taste to the anterior two-thirds of the tongue and somatic sensation to the external auditory meatus and postauricular region. Taste fibers synapse in the nucleus solitarius, while those of somatic sensation terminate in the spinal tract of the Vth nerve. Afferents to the facial nucleus are also derived from the trigeminal nucleus as part of the corneal reflex and the acoustic pathways as part of the stapedius reflex, in which the eyes blink reflexively to a loud noise (see later discussion).
Cerebellopontine angle . At the ventrolateral angle of the pons, the facial motor root and the vestibuloacoustic nerve exit the brainstem together. Between these two nerves lies the nervus intermedius carrying sensory and parasympathetic information. In the cerebellopontine angle, the anterior inferior cerebellar artery (AICA) courses between the VIIth and VIIIth nerves in its course to supply the lateral pons and anterior cerebellum. The close proximity of the Vth, VIIth, and VIIIth nerves in the cerebellopontine angle explains their involvement in tumors in this region. As the facial nerve motor branch enters the internal auditory meatus, it is joined to the nervus intermedius and lies superior and anterior to the vestibuloacoustic nerve. After exiting the internal auditory meatus, the facial nerves separate from the acoustic nerve to enter their own canal, the fallopian or facial canal ( Fig. 14.6 ). Here the facial nerve incorporates the geniculate ganglion and the first branch of the facial nerve known as the greater superficial petrosal nerve. This nerve travels forward along the floor of the middle cranial fossa to synapse in the sphenopalatine ganglion. Postganglionic parasympathetic fibers continue forward to innervate the lacrimal gland and nasopalatine glands.
At the level of the lateral semicircular canal, the nerve to the stapedius takes its origin at the proximal portion of this segment while the chorda tympani nerve branches off more distally. The chorda tympani nerve is a mixed nerve carrying taste fibers from the anterior two-thirds of the tongue, parasympathetic fibers to the submaxillary and sublingual glands, and pain and temperature sensation from the external auditory meatus.
Extracranial course . The motor branches of the facial nerve exit the skull base via the stylomastoid foramen. Nerve twigs are immediately provided to the posterior auricular, posterior belly of the digastric and stylohyoid muscles. The facial nerve then bends again to proceed forward to penetrate the posterior aspect of the parotid gland. Within the substance of the parotid gland, the facial nerve divides into upper and lower divisions. These divisions may be further subdivided from top to bottom into temporal, zygomatic, buccal, mandibular, and cervical branches (see Fig. 14.5 ). The vast interconnections among these branches provide the substrate for aberrant regeneration to ensue after facial palsy (see later discussion).
Vascular supply . From the brainstem to the internal auditory meatus, the facial nerve derives its blood supply from the anterior inferior cerebellar artery (AICA). The labyrinthine artery, a branch of the AICA, supplies the nerve in the internal auditory meatus. More distally, the petrosal branch of the middle meningeal artery enters the facial canal at the level of the geniculate ganglion and supplies blood to the tympanic portion of the nerve (see Fig. 14.6 ). Anastomotic connections are made to the tympanic region by the stylomastoid artery, which extends up the vertically oriented mastoid segment. The weakest link in the arterial supply to the facial nerve is just proximal to the geniculate ganglion, and this region represents the most likely site for ischemic injury to the nerve.
Muscles innervated by the facial nerve . All the muscles of facial expression are supplied by the facial nerve ( Fig. 14.7 ). The major muscles are the frontalis, which lifts the eyebrows; the orbicularis oculi, which closes the eyelids; the orbicularis oris, which closes the mouth and purses the lips; and the zygomaticus major, which lifts the angle of the mouth upward. The orbicularis oculi acts to close the eye and is organized in concentric circles around the orbital margin and the eyelids. There are three major parts of the orbicularis oculi: (1) the thick orbital part, for the most vigorous eyelid closure; (2) the thin palpebral and pretarsal portions, for closing the eyelids lightly (see Figs. 14.1 and 14.7 ); and (3) the lacrimal part, which pulls the eyelids and lacrimal puncta medially to aid tear flow.
History and Examination
When a patient complains of eyelid drooping, historical details such as duration, acuteness of symptoms, presence of eye pain, pupillary abnormalities, or diplopia are important considerations in making the diagnosis. Qualities such as fatiguability and associated dysarthria or swallowing or breathing difficulty may suggest underlying myasthenia gravis. Patients with eyelid retraction should be asked about symptoms such as temperature intolerance, tachycardia, or proptosis, which might indicate underlying thyroid-associated ophthalmopathy. Headache or difficulty with upgaze, consistent with a dorsal midbrain syndrome, should be queried. Individuals with facial palsy should be asked about medical conditions, such as diabetes, hypertension, sarcoidosis, Lyme disease, or pregnancy, which may predispose them to acquired VIIth nerve injury. In patients with abnormal blinking or facial movements, historical evidence of basal ganglia diseases, old Bell’s palsy, or multiple sclerosis, for example, should be investigated. A history consistent with allergies, photophobia, dry eye, or corneal damage may suggest an ocular cause of excessive eyelid closure.
Eyelid and facial nerve examination techniques . These are detailed in Chapter 2 . However, some important guidelines are discussed here. The eyelids and facial nerve should first be observed at rest. Eyelid position in relationship to the limbus and corneal light reflection should be noted and the palpebral fissures measured. The position of the nasolabial fold and the nostrils should be evaluated, because the nasolabial fold may disappear or be displaced in facial palsy, and the nostril may be ptotic or decreased circumferentially. Levator and orbicularis oculi function should be assessed. Facial nerve function can be tested by having the patient lift the eyebrows, close the eyelids, and smile.
Eyelid fatigue, curtaining, and lid twitch should be tested for if the eyelid is ptotic. Although these signs are suggestive of myasthenia gravis, they are not specific for the disease ( ). Hering’s Law of equal innervation, referring to the yoking of agonist muscles, applies to both levator muscles. Thus ptosis on one side may be accompanied by lid retraction on the other due to the excess tone required to keep the ptotic lid open ( Fig. 14.8A ). This is the case especially if the ptotic eye is the dominant and fixating one. In addition, if the ptotic eyelid is manually elevated, the retracted eyelid of the fellow eye drops (curtaining) ( Fig. 14.8B ). Similarly, when the ptosis is bilateral, if either eyelid is manually elevated, the ptosis on the other side worsens (enhanced ptosis) ( Fig. 14.9 ). Hering’s Law applies to ptosis caused by neuromuscular junction deficits as well as to ptosis resulting from oculomotor and other more proximal lesions. Conversely, there may be pseudoptosis associated with contralateral pathologic eyelid retraction ( Fig. 14.10 ).
The position of the involved eye’s eyebrow compared with that of the other eye may help differentiate between ptosis or spasm, both of which can reduce the width of a palpebral fissure. Because the frontalis muscle is usually contracted to elevate the eyelid to compensate for ptosis, the ipsilateral eyebrow in ptosis is typically elevated. In contrast, in blepharospasm, the ipsilateral eyebrow is typically lower, because the frontalis is relaxed and the orbicularis oculi is contracted.
The pupils and eye movements should also be observed due to the shared innervation of the eyelid, pupillary, and extraocular muscles. Examination techniques are detailed in Chapter 2 . In facial palsies, the ear should be examined for the presence of vesicles indicative of herpetic disease. When there are involuntary facial movements, the presence of subtle facial weakness or movements of other head and neck structures should be excluded. As suggested previously, corneal abrasion or ulceration, iritis with photophobia, blepharitis, and dry eye should be ruled out in patients with excessive blinking. The tarsal conjunctiva should be examined in all patients with ptosis and ocular irritation.
Physiologic blink reflexes . In the corneal blink reflex, bilateral eyelid closure is elicited by stimulating either cornea. This can be accomplished by touching the cornea with a wisp of cotton or by instilling an eye drop. The ophthalmic division of the trigeminal nerve (V1) is the afferent limb of this reflex, with first-order neurons synapsing primarily in the chief sensory nucleus within the pontine tegmentum. Second-order neurons project from the chief sensory nucleus to both facial nerve nuclei. There is a dose-response rate between the magnitude of corneal stimulation and blink latency. Tactile stimulation of the eyelids or eyelashes or tapping the forehead (glabellar reflex), which also elicit bilateral eyelid closure, are likely mediated by the same pathway. These reflexes normally habituate with repetitive stimulation. In the corneomandibular reflex, corneal stimulation elicits a bilateral eyelid blink and a brisk anterolateral jaw movement (palpebromandibular synkinesia).
The reflex blink to visual threat, useful for evaluating visual fields in young children or uncooperative adults, can be elicited by a threatening gesture such as a menacing hand. Care should be taken not to push air onto the cornea, thereby provoking a corneal blink reflex. The reflex blink to visual threat requires an intact afferent visual pathway and occipital lobe as well as parietal and frontal lobe areas which mediate visual attention. The reflex is likely a learned one, as infants younger than 2–4 months of age may not exhibit it. Patients in a vegetative state may have an intact blink to visual threat, so it is not clear whether consciousness is necessary for an intact response.
Other normal blink reflexes include blinking to sudden bright light or dazzle, which is entirely brainstem mediated. The afferent limb may be transmitted by either retinal ganglion cells or stimulation of trigeminal nociceptive pathways, with cortical modulation. In the acoustic blink reflex, the eyes blink reflexively to a loud noise.
Ptosis
Approach
The etiologies of ptosis should be considered according to age (congenital vs acquired in adulthood), abruptness of onset, the appearance of the eyelid, the severity of the ptosis, pupillary findings, and accompanying neurologic signs. Acquired, painless ptosis of sudden onset strongly suggests a neurologic cause such as Horner syndrome or IIIrd nerve palsy, especially in unilateral cases with pupillary involvement. Gradually progressive bilateral ptosis would be more consistent with a myopathic or neuromuscular junction disorder. Nonneurologic causes of ptosis, such as levator dehiscence, are more common than the etiologies listed above, and these disorders should be suspected in isolated cases. In addition, ptosis may be suspected incorrectly when, in fact, the upper eyelid of the other eye is pathologically retracted. When the ptosis is severe, a IIIrd nerve palsy or myasthenia gravis are the more likely etiologies, as the lid droop of a Horner syndrome, for instance, is quite mild.
Measurement of levator palpebrae superioris function is also frequently helpful in narrowing the differential diagnosis (see Fig. 2.22 ). Ptosis produced by levator dehiscence and Horner syndrome is usually associated with normal levator function. In contrast, levator function is reduced in ptosis associated with myasthenia gravis, congenital ptosis, IIIrd nerve palsies, and myopathic conditions.
A detailed differential diagnosis of ptosis is outlined in Box 14.1 , but this section will concentrate on the most common causes.
Congenital
Isolated
With double elevator palsy
Anomalous synkineses (including Marcus Gunn jaw-winking)
Lid or orbital tumors (hemangioma, dermoid)
Birth trauma (IIIrd nerve palsy, Horner syndrome)
Neurofibromatosis (neurofibroma)
Neonatal myasthenia (transient)
Congenital fibrosis syndrome
Acquired
Myogenic
Chronic progressive external ophthalmoplegia (CPEO)
Kearns–Sayre syndrome (CPEO “plus”)
Myotonic dystrophy
Oculopharyngeal dystrophy
Disorder of Neuromuscular Transmission
Myasthenia gravis
Lambert–Eaton syndrome
Botulism
Neurogenic
Horner syndrome
Oculomotor nerve palsy
“Cortical” ptosis
Obtundation, drowsiness, coma
Apraxia of eyelid opening
Mechanical
Inflammatory (edema, allergy, chalazion, hordeolum, blepharitis, conjunctivitis)
Cicatricial
Tumor (lid, orbit)
Blepharochalasis
Levator Dehiscence-Disinsertion Syndrome
Aging
Inflammation (ocular, lids, orbit)
Surgery (ocular, orbital, postcataract)
Trauma
Contact lens use
Pseudoptosis
Dermatochalasis
Duane’s retraction syndrome
Microphthalmos/phthisis bulbi
Enophthalmos
Pathologic lid retraction of the opposite eye
Chronic (old) Bell’s palsy
Voluntary blepharospasm
Hypotropia
Hysteria
Congenital
Isolated and with elevator palsy . Isolated, nonprogressive ptosis in a neonate or child is usually due to congenital maldevelopment of the levator palpebrae or its tendon. This also causes incomplete lowering of the eyelid in downgaze, resulting in lid lag ( Fig. 14.11 ). The upper eyelid crease is typically shallow or absent. Commonly the involved eye has superior rectus or complete elevator palsy, and if both eyes are ptotic, neither eye may have normal upgaze. This frequent association between the eyelid and motility deficit has been attributed to a common embryologic origin of and insult to the levator palpebrae and superior rectus muscles. Some studies have demonstrated myopathic or dysgenetic features in the levator muscle. Alternatively, a neurogenic cause such as a partial third nerve palsy has been proposed. Familial cases have been reported.
Marcus Gunn jaw-winking . Patients with Marcus Gunn jaw-winking have a ptotic eyelid, which retracts during contraction of the external pterygoid muscle (e.g., nursing, chewing, mouth opening, or moving the jaw forward or side to side), presumably from anomalous innervation of the levator by the trigeminal nucleus (trigemino-oculomotor synkinesis; and ). Cases are usually unilateral, but rarely patients are bilaterally affected. We have seen bilateral involvement where one eyelid was retracted and the other ptotic, and this pattern alternated when the child sucked a pacifier ( Fig. 14.12 ). Associated ophthalmologic abnormalities include amblyopia, superior rectus weakness, double elevator palsy, and anisometropia. Eyelid surgery can be considered when the jaw-winking or ptosis creates a functional or cosmetic problem.
Other congenital causes . Neurofibromas ( Fig. 14.13 ) and lid tumors such as hemangiomas should also be suspected in children with ptosis. Usually there is a palpable upper eyelid mass in these cases. Congenital oculomotor palsies (see Chapter 15 ), Horner syndrome (see Chapter 13 ), and congenital fibrosis syndromes (see Chapter 15 ) should also be considered in this age group. Ptosis in the pediatric population can be associated with strabismus or neurologic disease, so care must be taken to screen for these in any child presenting for evaluation of ptosis.
Acquired
Myopathic . Patients with myopathic ptosis often give a long history of droopy lids. Occasionally the ptosis will be the only manifestation of a myopathic condition. However, many patients have other neurologic signs. These patients often have levator function between 5 and 11 mm. Important myogenic causes of ptosis include the mitochondrial disorders chronic progressive external ophthalmoplegia (CPEO) and Kearns–Sayre syndrome (KSS), myotonic dystrophy, and oculopharyngeal dystrophy. These entities are discussed in detail at the end of this chapter.
Neuromuscular junction . Fatigable or variable unilateral or bilateral ptosis suggests a disorder of neuromuscular transmission, such as myasthenia gravis, Lambert–Eaton myasthenic syndrome (LEMS), and botulism. These are also discussed in detail at the end of this chapter.
Neuropathic . IIIrd nerve palsy . Prominent unilateral ptosis with decreased levator function, adduction, elevation, and depression deficits, with or without pupillary mydriasis, suggests an infranuclear IIIrd nerve palsy (see Chapter 15 ). A posterior communicating aneurysm manifesting as unilateral ptosis in isolation is rare. A unilateral nuclear oculomotor lesion often causes bilateral ptosis (nuclear ptosis), worse ipsilaterally, ipsilateral IIIrd nerve dysfunction, and contralateral superior rectus weakness due to the arrangement of the subnuclei within the midbrain (see Chapter 15 ).
In the setting of a resolved IIIrd nerve palsy, a ptotic eyelid which elevates (retracts) when the eye infraducts or adducts implies aberrant regeneration of the eyelid. This levator synkinesis phenomenon is discussed in more detail in Chapter 15 .
Horner syndrome. Mild unilateral ptosis with normal levator function, accompanied by miosis and pupillary dilation lag in the dark, implies Horner syndrome (see Chapter 13 ). The ptosis never completely covers the eye in Horner syndrome. The lower eyelid may be elevated in so-called lower eyelid ptosis. The small palpebral fissure due to the combination of the upper and lower eyelid ptosis gives the eye a pseudoenophthalmic appearance.
Cerebral (or cortical) ptosis. A unilateral cerebral hemispheric lesion may uncommonly cause unilateral or bilateral ptosis without IIIrd nerve or sympathetic involvement or apraxia (see later discussion). The side of the unilateral ptosis or the lower lid in bilateral cases can be either ipsilateral or contralateral to the lesion. The ptosis is usually transient, lasting only for a few days. In a series of 13 patients with bilateral cerebral ptosis, all patients had an acute right frontotemporoparietal lobe lesion and conjugate gaze deviation to the right. Three other patients with right-sided lesions were reported who had bilateral ptosis and upgaze palsy. These and other similar observations suggest some supranuclear cortical control of the levator muscles, perhaps with right hemispheric dominance.
Apraxia of eyelid opening. Nonparalytic, deficient voluntary eyelid elevation ( apraxia of eyelid opening ) can mimic levator paralysis until the patient opens the eyes without ptosis after a sudden command or stimulation. Patients contract their frontalis muscles while attempting to open their eyes. No ocular myopathy or sympathetic dysfunction is present. This disorder should be distinguished from blepharospasm, which often accompanies it. In blepharospasm (see the section Facial Nerve ) there is obvious contraction of the orbicularis oculi, which does not visibly occur in apraxia of eyelid opening. However, in some patients with apraxia of eyelid opening, there may be electromyographically demonstrable (but not visible) orbicularis oculi contractions of the pretarsal portion during attempted eyelid opening.
Apraxia of eyelid opening occurs insidiously in association with extrapyramidal disorders such as progressive supranuclear palsy (PSP) ( ), Parkinson’s disease (PD), Shy–Drager syndrome, Huntington disease, and Wilson disease. Rarely this disorder can be seen in association with subthalamic nucleus deep brain stimulation for Parkinson’s disease and paraneoplastic anti-Ma and anti-Hu encephalitides, acutely with dominant and nondominant hemispheric lesions, bifrontal lobe disease, and chronically with amyotrophic lateral sclerosis. Benign, idiopathic forms have been reported. The exact lesions responsible for apraxia of eyelid opening are uncertain, and there are likely multiple pathways involved.
In patients with pyramidal and extrapyramidal diseases, some authors have questioned the use of the term apraxia, which should be used only in the context of intact motor systems. Therefore, a more appropriate term such as “involuntary levator palpebrae inhibition of supranuclear origin” has been suggested. Others have termed it an eyelid dystonia, particularly if abnormal orbicularis oculi contraction is implicated.
Botulinum injections into the pretarsal portion of the orbicularis oculi are sometimes recommended, based upon the motor persistence of this muscle alluded to previously. Levodopa has been used in some isolated cases. Upper eyelid myectomy has been performed in patients with blepharospasm with associated apraxia of eyelid opening refractory to botulinum toxin treatment.
Levator dehiscence-disinsertion syndrome (aponeurotic ptosis) . This is the most common cause of acquired ptosis in adults. In many elderly patients the aponeurosis of the levator muscle may spontaneously dehisce or disinsert from the tarsal plate of the upper eyelid ( Fig. 14.1A ). The upper eyelid crease is often high (further from the eyelid margin) or indistinct, and levator function is relatively preserved ( Fig. 14.14 ). In younger and middle-aged patients, the most common etiology of levator dehiscence is eyelid manipulation in association with contact lens wear, more often with hard rather than soft lenses. Eyelid manipulation during lens removal is thought to cause or exacerbate the disinsertion, but pathologic studies have also shown fibrosis of Müller’s muscle. Other important causes of levator dehiscence include trauma, ocular surgery (such as cataract or orbital surgery), allergies, and eyelid edema.
Pseudoptosis . Disorders in this group are characterized by an eyelid that falsely appears to be drooping and therefore mimics ptosis. The various causes are listed in Box 14.1 , but the most important ones include contralateral lid retraction and ipsilateral eyelid relaxation secondary to Hering’s Law (see Fig. 14.10 ), enophthalmos, hypotropia, and dermatochalasis, the hanging of skin over the eyelid due to loss of skin elasticity, and orbital fat herniation.
Treatment
Other than treating the primary cause, ptosis can be managed by taping the eyelids open or with eyelid “crutches” attached to eyeglasses. Most patients find the latter uncomfortable. Surgical management of ptosis is more effective in chronic cases, and popular procedures include shortening of the levator muscle or aponeurosis, Müller’s muscle resection, and frontalis suspension.
Eyelid Retraction
In primary gaze, the upper eyelid normally reaches just below the limbus. Eyelid retraction is diagnosed if there is sclera showing between the lower edge of the upper or lower eyelid and the upper or lower limbus. Box 14.2 lists a differential diagnosis of eyelid retraction. The three most important neuro-ophthalmic causes of eyelid retraction are thyroid-associated ophthalmopathy, dorsal midbrain lesions, and contralateral ptosis. This section discusses the first two. Eyelid retraction due to contralateral ptosis is a consequence of Hering’s Law and has already been discussed. Based on this relatively small differential diagnosis, we recommend that any patient with acquired eyelid retraction without contralateral ptosis or known thyroid disease undergo thyroid function testing (TFT). If the thyroid workup is unrevealing, or if there is a history of headache, blurred vision, or ataxia, and there are other signs of dorsal midbrain disease, then neuroimaging of the brain is warranted.
Neurogenic
Dorsal midbrain syndrome
Collier’s eyelid retraction
Eyelid lag in downgaze
Contralateral ptosis
Marcus Gunn jaw-winking
Aberrant regeneration of the IIIrd nerve
Ocular neuromyotonia
IIIrd nerve palsy with cyclic spasms
Facial nerve paresis
Eyelid nystagmus
Extrapyramidal disease
Ipsilateral superior rectus weakness and enhanced innervation to the superior rectus/levator complex
Hypokalemic and hyperkalemic periodic paralysis
Myogenic
Thyroid-associated ophthalmopathy (Graves)
Congenital
Mechanical
Proptosis
Axial myopia
Ocular or orbital surgery
Eyelid scarring
Thyroid-Associated Ophthalmopathy
Upper eyelid retraction may be the only ocular abnormality in these patients. The retraction can either be unilateral or bilateral ( Fig. 14.15A ). The eyelid tends to more retracted temporally than medially. The exact mechanism of the eyelid retraction is unclear, but (1) fibrous contraction, thickening, shortening, or hyperactivity of the levator palpebrae muscle; (2) sympathetic overdrive and overaction of Müller’s muscle; (3) proptosis; and (4) secondary upper eyelid retraction due to a restricted inferior rectus and limited upgaze have all been proposed as contributory factors. Retraction is often accompanied by lid lag (von Graefe’s sign), in which the upper eyelid fails or is slow to follow the eye in downgaze ( Fig. 14.15B ). In thyroid-associated ophthalmopathy, the etiology of lid lag is likely related to the causes of the lid retraction. The lower lid is also frequently retracted.
Exposure keratopathy and dry eye can complicate thyroid-related lid retraction and lag, especially in individuals with infrequent blinking. Artificial tears are usually sufficient, but some thyroid patients with lid retraction require surgical levator recession or division, aponeurosis division, or excision of Müller’s muscle.
Further details regarding the features, diagnosis, and management of thyroid-associated ophthalmopathy are discussed in Chapter 18 .
Pretectal Eyelid Retraction (Collier’s Sign)
Eyelid retraction may be a prominent sign in pretectal (or Parinaud or dorsal midbrain) syndrome. The patients have a characteristic stare ( Fig. 14.16 ), often accompanied by upgaze paresis. The lid retraction is typically symmetric, except in the plus–minus lid syndrome (see later discussion). Also, it usually is exacerbated on attempted upgaze, and normally the lids relax on downgaze. However, in some exceptional instances there is lid lag in downgaze (see later discussion).
The other elements of the pretectal syndrome, which include supranuclear vertical gaze paresis ( Chapter 16 ), pupillary light-near dissociation ( Chapter 13 ), and convergence retraction nystagmus ( Chapter 17 ), are discussed elsewhere.
Because the lid retraction typically occurs in patients with upgaze paresis, some authors have attributed the finding to combined excess superior rectus innervation and levator activity. However, Schmidtke and Büttner-Ennever postulated that neurogenic lid retraction can result either from a unilateral lesion of the nPC or from interruption of the posterior commissure, both of which would result in decreased inhibition of levator neurons in the CCN (see Fig. 14.2 ).
Eyelid lag in downgaze . As described earlier in this chapter, eyelid position is normally coordinated with vertical eye movements so that in upgaze the eyelids elevate, and in downgaze the eyelids typically relax and fall. In dorsal midbrain lesions, this relationship can be disrupted, causing the eyelids to remain elevated while the eyes infraduct. Dramatic examples include the setting-sun sign (tonic downward eye deviation with lid retraction) in infants with hydrocephalus, thalamic hemorrhage (see Chapter 16 ), and rare comatose patients with phasic vertical eye movements and persistent eyelid elevation. Lid lag in some instances may be difficult to detect because patients with pretectal dysfunction may have downgaze paralysis early in their course that precludes the ability to detect lid lag.
Although lid lag and lid retraction in such instances may share the same mechanism, patients have been observed who do not have lid retraction in primary gaze but have lid lag in downgaze ( Fig. 14.17 ). This suggests there may be separate central mechanisms for these eyelid abnormalities. One possible lesion for lid lag without retraction involves the inhibitory connections from the supranuclear downgaze centers to the central caudal nucleus, most likely involving the M-group neurons (see Fig. 14.2 ).
Plus–minus eyelid syndrome . A unilateral lesion involving nPC and the oculomotor fascicle would produce an ipsilateral IIIrd nerve palsy with ptosis and contralateral lid retraction (plus–minus lid syndrome) ( Fig. 14.18 ). The ipsilateral lid retraction is masked by the infranuclear IIIrd nerve palsy. This eyelid pattern of ptosis and contralateral lid retraction can be mimicked in an individual with ptosis who fixates with the ptotic eye, thereby increasing the innervation to both levators (Hering’s Law). In this case manual elevation of the ptotic eyelid would eliminate the contralateral lid retraction. It may also be seen in a patient with ptosis and contralateral superior rectus weakness who is fixating with the nonptotic eye and increasing the innervation to the levator–superior rectus complex. This possibility can be investigated by covering the fixating nonptotic eye.
Miscellaneous Causes
Eyelid retraction in association with Marcus Gunn jaw-winking and aberrant regeneration of the IIIrd nerve with levator synkinesis have already been mentioned in the section on ptosis. Other neuro-ophthalmic causes include extrapyramidal diseases, neuromyotonia, and oculomotor paresis with cyclic spasm (see Chapter 15 ). Mechanistic etiologies such as proptosis, axial myopia, eyelid scarring, and ocular or orbital surgery (such as overcorrection of ptosis) should be considered. A congenital, idiopathic variety has also been described.
Facial Weakness
Although idiopathic Bell’s palsy is a common cause of facial weakness, it is important to explore the differential diagnosis of facial palsies. This was emphasized in a study by Hohman, in which only 38% of patients in a facial nerve referral practice had Bell’s palsy. Other supranuclear, nuclear, infranuclear, and neuromuscular causes of facial weakness must be considered, as Bell’s palsy is a diagnosis of exclusion.
Approach
When weakness of the face is present, determining whether the palsy is central or peripheral is the first important diagnostic consideration. Asking the patient to look up or raise the eyebrows causes contraction of the frontalis muscle. If frontalis function is intact, a central palsy is likely, while impaired frontalis contraction suggests a peripheral cause ( Fig. 14.19 and and ; see also Fig. 14.3 ).
