SIGNS AND SYMPTOMS

Gaze stability mechanisms: from vestibular apparatus (labyrinthine) with a short latency (<16 msec vs. visually mediated movements that have >70 msec latency). Combined movements of head and eye require cancellation of the vestibulo-ocular reflex (VOR).

Angular movement: mediated by the semicircular canals responsible for torsional motion. Vestibular input projects ipsilaterally to the MVN, then to the contralateral PPRF and CN VI nucleus, then back across the midline to the ipsilateral MLF and CN III nucleus. Also controlled by midline cerebellar structures (anterior vermis) and cervical neck receptors.

Example: a head turn to the right stimulates the right semicircular canals and thus stimulates the left CN VI nucleus and the left LR and the right CN III nucleus and the right MR, with the result that the eyes turn to the left.

Destruction of vestibular apparatus causes the opposite inner ear to stimulate gaze toward the side of the lesion.

Linear movement: mediated by the otoliths (utricle and saccule), concerned with translational motion.

Gaze-shifting mechanisms: primarily from visually mediated mechanisms (pursuit, optokinetic, vergence); supplement the VOR and stabilize the gaze during sustained head movements (e.g., optokinetic nystagmus and full-field movement) and VOR (e.g., brainstem function and doll’s eyes).

Vergence movements: arise from midbrain control and include fusional vergences, resting state, and horizontal and vertical vergences. Other

horizontal vergence movements include accommodative for near work, tonic for everyday use, and proximal or instrument (e.g., when looking through a microscope).

Table 8–1 presents a comparison of the sympathetic and parasympathetic autonomic nervous system.

Signs and Symptoms

ABERRANT REGENERATION Seen with axons that become misdirected during the repair phase, such as that following CN III palsy from trauma, tumor, or aneurysm (but not ischemia). May manifest as crocodile tears, Adie’s pupil, pseudo-Graeffe’s sign (lid elevation with down gaze), and pseudo–Argyll Roberston pupil. Distinguish from dyskinesis.

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AFFERENT PUPILLARY DEFECT (APD) Usually from unilateral or asymmetric ON disease. Mild APD may also be seen with contralateral optic tract damage (52% of chiasmal fibers cross) or contralateral pupillomotor fiber damage in the midbrain. ON may lose 40 to 50% of fibers before APD develops and does not show a change in pupil size.

ANISOCORIA Asymmetric pupil size (>1 mm of difference between the eyes). Figure 8–6 shows flowchart for amiscoria dignosis.

Anisocoria greater in light (larger than normal pupil): suggests parasympathetic paresis such as that seen in Adie’s tonic pupil, CN III lesion (e.g., uncal herniation), postictal seizures, migraine, siderosis, or pharmacologic reactions. A larger pupil may also be seen with acute glaucoma, iris trauma, or sympathetic hyperactivity.

Adie’s pupil: parasympathetic denervation in the ciliary ganglion with aberrant regeneration of the fibers that normally travel to the ciliary body to control accommodation now innervating the iris sphincter. Thus, patients have light-near dissociation and vermiform iris movements. The iris is hypersensitive to weak pilocarpine; if acute, may not constrict to pilocarpine and may mimic pharmacologic dilation.

Figure 8–6 Anisocoria flowchart for diagnosis.

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Fixed dilated pupil: symptomatic of pharmacologic reactions (ask about ‘‘red cap’’ drops, look for a scopolamine patch for motion sickness, consider functional diagnosis), Adie’s pupil, CN III lesion (uncal herniation obvious; otherwise, rare; check angiogram), and migraine.

Anisocoria greater in dark (smaller than normal pupil): suggests sympathetic lesion such as that seen in Horner’s syndrome, cluster headache, or pharmocologic reaction. May also be from hyperactive parasympathetic system such as cyclic oculomotor paresis (miosis during the spastic phase).

Horner’s syndrome: ptosis (and reverse ptosis), miosis, anhydrosis, enophthalmos, decreased tearing, and heterochromia if congenital. Cocaine blocks norepinephrine reuptake and causes normal pupil dilation if the sympathetic chain is intact; however, in Horner’s syndrome, no norepinephrine is present in the nerve endings, and thus dilation does not occur. If cocaine test is positive, may perform Paredrine (hydroxyamphetamine) test at least a day later to localize the Horner’s syndrome to a first or second order neuron pathway versus a third order. Paredrine stimulates release of norepinephrine and thus causes pupil dilation if third order neuron is intact. More dilation than normally seen with aproclonidine may also suggest alpha-1 hypersensitivity.

First order neuron: usually obvious neurologic cause from brainstem disease.

Second order neuron: usually C-spine trauma or tumor, or apical lung tumor (Pancoast’s tumor).

Third order neuron: carotid artery dissection or neck surgery, cavernous sinus lesion, nasopharyngeal CA, migraine, orbital disease or Raeder’s trigeminal neuralgia.

Other causes of anisocoria or pupil abnormalities:

Argyll Robertson pupil: miotic and irregular pupil associated with light-near dissociation, tertiary syphilis.

Behr’s pupil: larger pupil seen on side of hemianopia.

Cheyne-Stokes pupil: associated with terminal respiratory pattern.

Hutchinson’s pupil: seen in comatose patients.

Traumatic: sphincter tear causing mydriasis.

Wernicke’s pupil: associated with optic tract disease.

Testing for anisocoria: see Table 8–2 for pharmacologic testing for anisocoria.

COMPRESSIVE OPTIC NEUROPATHY Usually from tumor (especially glioma or meningioma), orbital mass, or myopathy. Often presents with progressive loss of vision, and usually disk pallor or atrophy, but can present with unilateral edema.

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306 NEUROLOGIC

TABLE 8–2

Pharmacologic Testing for Anisocoria

CONGENITAL DISK ELEVATION Hemangioma or congenital anomalous optic disk.

CONSTRICTED VISUAL FIELD Bilateral occipital lobe infarcts with macular sparing, RP, glaucoma, chronic papilledema, or functional.

DIPLOPIA, BINOCULAR Strabismus, prism in glasses.

DIPLOPIA, MONOCULAR Dry eye, astigmatism or refractive error, cataract, corneal scarring, blepharitis, polycoria, CME/ICSR/ERM, ARC following strabismus surgery (rare), palinopsia, cerebral polyopia (ischemic occipital lobe), psychogenic.

DISEASES INVOLVING THE ON DUSN, ARN, GCA, VKH, sarcoidosis, toxoplasmosis, CMV, syphilis, sympathetic ophthalmia, Wegener’s granulomatosis, toxocariasis, papillophlebitis, AMPPE, Leber’s neuroretinitis, scleritis, Behc¸et’s syndrome, SLE, CRAO, papillitis, CRVO, and ischemic optic neuritis.

DYSKINESIS Congenitally misdirected nerve axons, as in Duane’s syndrome and Marcus Gunn jaw winking. Differentiate from aberrant regeneration.

HEADACHE DIFFERENTIAL DIAGNOSIS

Hypertension: usually seen in patients ages 40 to 50.

Encephalgia: migraine usually with positive family history, seen in patients ages 20 to 30; may be classic ‘‘sick headaches’’ with aura, visual phenomenon, and nausea, or complicated with other neurologic signs, or may be acephalgic.

Arteritis: GCA

Definite headache syndromes: trigeminal neuralgia with sharp uni-

lateral pain affecting CN V3 > CN V2 > CN V1, lasting seconds, usually seen in older F > M patients; Gradenigo’s syndrome with CN

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V or CN VI pain from ear infection; postherpetic neuralgia; temporomandibular joint disease.

Ocular etiology: asthenopia, uveitis, dry eye, optic neuritis, vascular

Cervical spine: suboccipital headache

‘‘Head bone’’: intracranial tumors, subdural hematoma (SDH), aneurysm, hydrocephalus. Other intracranial causes of headache that should not be missed include:

Intracranial hemorrhage: severe headache, focal neurologic defect

Pituitary apoplexy, Sheehan’s syndrome: postpartum pituitary infarction, hypocalcemia, acromegaly

Subarachnoid hemorrhage: worst headache patient has had, stiff neck, usually from trauma or aneurysm

Carotid artery dissection: may have Horner’s syndrome plus ipsilateral headache; check MRA.

Meningitis: nucal rigidity, Lhermitte’s sign, photophobia

Ear, nose, and throat (ENT) causes: ear infection, frontal sinusitis (often has pain in the morning), maxillary sinusitis (often has pain in the evening)

Psychogenic: consider last because it is a rule-out diagnosis; history of stress.

HETEROCHROMIC IRIDES Fuchs’ HIC, long-standing uveitis, congenital Horner’s syndrome (involved side is hypochromic) or neuroblastoma causing Horner’s, leukemia, chronic IOFB, JXG, prostaglandin analogue drops, HZV, Waardenburg’s syndrome, idiopathic.

LESION LOCALIZATION Ocular signs and symptoms from CNS lesions (stroke, tumor, trauma):

Frontal lobe lesions: tonic eye deviation from involvement of frontal eye fields (controls saccades). Patient looks toward destructive lesions and away from an irritative (seizure) focus. Doll’s eyes remain intact.

Occipital lobe disease (i.e., posterior cerebral artery infarction): may manifest as quadrantic homonymous hemianopsia, macular sparing (if posterior pole of the occipital lobe is spared; usually has normal VA), monocular temporal crescent (if anterior pole is spared), checkerboard

field, ipsilateral facial pain (V1), or loss of high spatial frequency or contrast sensitivity; vision may be blurred despite 20/20, micropsia, macropsia, metamorphopsia, or unformed visual hallucinations. Cortical blindness after cardiac arrest is most often from watershed infarct of the occipital lobe tips.

Occipitotemporal lesion, medial, bilateral: prosopagnosia (difficulty recognizing familiar faces)

Parietal, dominant lobe (visual association areas, Brodmann’s areas 18, 19; i.e., from left posterior cerebral artery infarction): alexia without

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308 NEUROLOGIC

agraphia (reads but cannot write), visual agnosia (sees the image but without meaning), optic agnosia (cannot say name of identified object)

Gerstmann’s syndrome: left-right confusion, finger agnosia, dysgraphia, dyscalculia.

Parietal, nondominant lobe (visual association areas; i.e., from right posterior cerebral artery infarction): prosopagnosia, visual hemifield agnosia, hemineglect

Parietal, bilateral (visual association areas; i.e., from left and right posterior cerebral artery infarction): cortical blindness, usually not simultaneous; pupil reflex is still present. Patients may also have achromatopsia, loss of stereopsis, and stepwise return of vision (motion perception returns first, then LP, color, central vision, then last visual association). Riddoch’s phenomenon observed if patients are blind but able to perceive objects in motion.

Anton’s syndrome: patients deny being blind.

Balint’s syndrome: bilateral posterior parietal stroke causing pychic paralysis of gaze (ocular apraxia, unable to make voluntary eye movements but spontaneous movements intact), simultanagnosis (difficulty processing more than one thing), and optic ataxia (difficulty looking at more than one thing).

Temporal lobe disease: formed visual hallucinations

LIGHT-NEAR DISSOCIATION Wernicke’s syndrome, Argyll Robertson pupil, Parinaud’s dorsal midbrain syndrome/posterior communicating artery (PCA) infarct pinealoma, and diabetes. Also caused by aberrant regeneration of CN III, Adie’s tonic pupil, amyloidosis, Charcot-Marie- Tooth syndrome.

MACRODISKS (area >4.09 mm) Physiologic, congenital ON pit, morning glory anomaly, congenital glaucoma, high myopia

MICRODISKS (area <1.29 mm) Pseudopapilledema, ON drusen, nonarteritic AION, ON hypoplasia, high hyperopia

OPTIC DISK ATROPHY Trauma, compressive (mass, chronic hydrocephalus), advanced retinal diseases (e.g., RP, CRAO), postpapilledema, pseudotumor cerebri, genetic.

Schnable’s optic atrophy: optic nerve cupping with atrophy; pathology shows cavernous spaces in the anterior nerve, possibly containing vitreous or MPS; not caused by glaucoma. A description, not a functional term; makes good histopathology photos for examinations.

OPTIC DISK EDEMA Determine if the edema is papilledema (almost always bilateral), a unilateral swollen disk, or pseudopapilledema.

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Papilledema: passive optic disk swelling secondary to increased intracranial pressure (ICP); bilateral but may be asymmetric (and an atrophic nerve cannot swell). The first sign is loss of spontaneous venous pulsations (SVPs), along with swelling of the nasal disk, then ‘‘doughnut ring’’ disk swelling with preservation of the physiologic cup (unlike pseudopapilledema) and increased capillarity. MRI is 90% sensitive for the diagnosis. Visual field first shows increased blind spot, then nasal field defect (usually inferior), progressing to arcuate scotoma, then constricted fields and potentially NLP vision. Usually from trauma, idiopathic intracranial hypertension, mass effect (tumor, etc.), or meningitis. See also VINDICTIVES etiologies below.

Acute: flame hemorrhages, CWS, ‘‘pink’’ disk, dilated and tortuous vessels

Subacute: early disk paleness, resolving hemorrhages

Chronic: mildly elevated, pale, ‘‘champagne cork’’ appearance with Paton’s lines (‘‘high water’’ marks), poor vision, and tunnel visual field

Pseudopapilledema: no CWS or hemorrhage, unlike papilledema, and disk has loss of physiologic cup with scalloped disk borders. Often used synonymously with ON drusen, but may also be associated with hyperopia, myelinated NFL, or tilted disk.

Swollen disc: unilateral disk edema with or without vision loss; usually with enlarged blind spot secondary to elevated retina (hyperopic shift). Often from anterior optic neuritis, nonarteritic anterior ischemic optic neuropathy (NAION) or arteritic ION, papillophlebitis, compressive optic neuropathy, infiltrative, malignant hypertension, toxic reaction (oral contraceptives, vitamin A, ethambutol, etc.). Mnemonic describes other etiologies: VINDICTIVES: vascular (CHF, dural sinus thrombosis), idiopathic/iatrogenic (radical neck dissection), neoplasm (carcinomatous meningitis, leukemia), drugs, immune response, congenital, trauma, infection, vascular, endocrine (eclampsia), systemic.

OPTIC DISK PALLOR Ischemic optic neuropathy after the acute phase, prior optic neuritis, infiltrative, compressive (TRIO, mengioma, etc.), carcinomatous, toxic response, nutritional, hereditary, radiation

ON ABNORMALITIES WITH SEROUS RD ON coloboma, morning glory anomaly, juxtapapillary staphyloma, ON pit

ON INFECTIONS Syphilis, Bartonella, tuberculosis, Lyme disease (papillitis occurs late in the course of the disease, with photophobia, pain)

ON INFILTRATIVE LESIONS Lymphoma, leukemia, malignant histiocytosis, plasmacytoma, sarcoidosis

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