Common Neuro-Ophthalmic Pitfalls (Case-Based Teaching)

Description

Using real-life cases describing patients with neuro-ophthalmic disorders, this book is a case-based teaching tool that bridges the gap between textbook information and everyday clinical practice. Each case illustrates a particular area of frequent diagnostic confusion, and highlights the specific clinical features that should point to the correct diagnosis. Focusing on errors in this way serves as motivation to the clinician to master the material so that 'pitfalls' can be avoided. The level of the case discussions assumes that the reader has some familiarity with basic neuroanatomy, physiology and disease process but each case discussion furnishes a brief review of such information, always with an emphasis on those features that are clinically relevant. The case-histories are succinct and amply illustrated, including motility and fundus photographs, visual fields and radiographic studies. The narrative is moved along with questions to the reader, making it easy to follow the logic of the cases. Cover Half-title Title Copyright Contents Foreword Preface Acknowledgements 1 When ocular disease is mistaken for neurologic disease Double images What important piece of historical information is still missing in this case? What maneuver might be helpful for confirming our suspicion that this patient’s double vision is ocular in nature? Diagnosis: Monocular diplopia due to cataract Headache and bilateral disc edema What test was done and what was the diagnosis? Diagnosis: Malignant hypertension Chronic optic neuropathy Having excluded compressive, inflammatory and infiltrative causes of optic neuropathy, what othermechanisms would you consider? How would you proceed? Diagnosis: Glaucomatous optic neuropathy Painful mydriasis What clues suggest an alternative diagnosis? Diagnosis: Acute angle closure glaucoma Invisible retinal disease Twinkling scotoma What aspect of this patient’s positive visual phenomenon is highly atypical for migraine? Diagnosis: Acute idiopathic blindspot enlargement Sudden monocular visual loss with normal fundus What othermechanism of visual loss would you consider? Are there any historical features that are helpful here? Whymight a retinal stroke not have been apparent on examination? Hazy night vision What specific aspect of this patient’s history suggests the correct localization of his visual problem? Diagnosis: Hypovitaminosis A Swirling vision Diagnosis: Cancer-associated retinopathy Episodic monocular blur This patient’s work-up addressed the possibility of retinal vascular disease as the cause of his transientmonocular visual loss (TMVL). Is there something about his history, however, to suggest a different mechanism for his episodes? Diagnosis: Transientmonocular visual loss due to corneal decompensation FURTHER READING Monocular diplopia Hypertensive retinopathy Twinkling scotoma Central retinal artery occlusion Hypovitaminosis A Cancer-associated retinopathy Corneal decompensation Glaucoma 2 When orbital disease is mistaken for neurologic disease Incidental elevation deficit What othermechanism could account for this patient’s abnormal ocularmotility besides a third nerve palsy? Diagnosis: Orbital floor fracture with muscle entrapment Painless vertical diplopia What clinical features help to localize the source of this patient’s ocularmotility disorder? Diagnosis: Euthyroid Graves’ disease Fatigable ptosis How is lid fatigability objectively demonstrated? What other forms of ptosismight share a similar history of worsening with sustained use? Diagnosis: Levator dehiscence Painful ptosis and diplopia What is the anatomic significance of a superior division palsy? The investigation thus far has revealed no intracranial pathology. How would you proceed? Diagnosis: Idiopathic orbitalmyositis Painful optic neuropathy Is this patient’s clinical course consistent with a diagnosis of optic neuritis? What specific feature of her clinical course raises the possibility of orbital disease? Diagnosis: Idiopathic optic perineuritis FURTHER READING Orbital examination and restrictive orbitopathy Levator dehiscence Painful ptosis and diplopia Optic perineuritis 3 Mistaking congenital anomalies for acquired disease Headaches and elevated discs Inferior altitudinal visual field defects Are there clues to the correct diagnosis in this case? Diagnosis: Superior segmental hypoplasia Incidental abduction deficit What feature identifies this woman’s abduction deficit as a congenital, rather than acquired, sixth nerve palsy? Diagnosis: Type I Duane’s syndrome Intermittent vertical diplopia What other causes of fourth nerve palsy should be considered? How would you pursue a diagnosis of congenital fourth nerve palsy in this patient? Diagnosis: Congenital fourth nerve palsy FURTHER READING Pseudopapilledema Superior segmental hypoplasia Duane’s syndrome Congenital superior oblique palsy 4 Radiographic errors Ordering the wrong scan Progressive optic neuropathy Is there a problem with the diagnosis of “chronic optic neuritis”? What clinical features in this case suggest the likely mechanism of her chronic optic neuropathy? What additional radiographic evaluation should be obtained? Diagnosis: Optic nerve sheathmeningioma Headache and papilledema Diagnosis: Cerebral venous sinus thrombosis Idiopathic ptosis and miosis Why is the current study incomplete? Diagnosis: Postganglionic Horner syndrome Subtle radiographic findings "Boxer" ptosis The above clinical findings are characteristic of a postganglionic Horner syndrome. Howmight this be related to her preceding trauma? Diagnosis: Internal carotid artery dissection Headache and bilateral third nerve palsy What is the diagnosis? What confirmative study would you order? Diagnosis: Pituitary apoplexy Progressive sixth nerve palsy What aspect of this patient’s presentation provides the most compelling diagnostic clue? Diagnosis: Petrous ridge meningioma Midline and bilateral abnormalities Bilateral idiopathic sixth nerve palsy Is a diagnosis of vasculopathic sixth nerve palsy still tenable here? What are the most common causes of bilateral sixth nerve palsy and what mechanism ismost likely in this case? Diagnosis: Clivus tumor Atypical pseudotumor cerebri syndrome What features of this case are atypical for a diagnosis of IIH? What alternative diagnosis should be considered? Diagnosis: Superior sagittal sinus thrombosis Vertical diplopia Diagnosis: Symmetric Graves’ disease FURTHER READING Neuro-imaging Canalicular meningioma Cerebral venous thrombosis Horner syndrome and carotid dissection Chronic sixth nerve palsy 5 Incidental findings (seeing but not believing) Empty sella Low cerebellar tonsils Sphenoid sinus mucocele Dolichoectatic basilar artery FURTHER READING Pseudotumor cerebri syndrome Chiari malformation Sphenoid sinus mucocele Dolichoectatic basilar artery 6 Failure of pattern recognition Painful ophthalmoplegia Where is this patient’s lesion? Diagnosis: Tolosa Hunt syndrome Painful ophthalmoplegia and visual loss Based on the clinical findings, where is the lesion? Diagnosis: Orbital apex syndrome Painless diplopia What is thismotility pattern, and what does it tell you about the mechanism of the patient’s diplopia? Diagnosis: Oculomotor nerve palsy with aberrant regeneration Right-sided visual field loss What is the significance of this visual field pattern? Does it help to illuminate the findings on her MRI? Diagnosis: Lateral geniculate body stroke FURTHER READING Painful ophthalmoplegia Orbital apex syndrome Third nerve misdirection Lateral geniculate body 7 Clinical findings that are subtle Painless central gray spot in a teenager What is the most likely cause of this patient’s neuroretinitis, and how would you test for it? Diagnosis: Neuroretinitis due to cat scratch disease Chronic "pink eye" This patient had an additional non-ocular symptom which she did not volunteer because she didn’t think it was relevant to her eye problem, yet this symptom was an important clue to the correct diagnosis. What question should be asked? Diagnosis: Dural-cavernous fistula Bouncing vision What is her symptom of “bouncing vision” called and what physical finding would you look for on examination? This patient’s eye examination, however, was normal, specifically nystagmus was not observed. Why not? What examination techniques can help in the detection of nystagmus when the oscillatory amplitude is particularly small? Diagnosis: Downbeat nystagmus due to Chiari I malformation Farmer with an adduction deficit Diagnosis: Myasthenic pseudo-INO FURTHER READING Neuroretinitis Dural-cavernous fistula Downbeat nystagmus 8 Misinterpretation of visual fields Abnormal field and night blindness How would you describe this patient’s visual field defect? What diagnoses should be considered? Diagnosis: Retinitis pigmentosa Constricted fields after herniation What bedside test can help distinguish non-organic field loss from true constriction of the visual field? Diagnosis: Bilateral occipital stroke with macular sparing Sudden difficulty reading the paper What simple “bedside” test could be performed to further investigate this patient’s symptom? Diagnosis: Small homonymous scotoma due to occipital stroke Post-cardiac bypass visual loss Is there another possible explanation for this patient’s visual loss, and how would you investigate this alternative mechanism? Diagnosis: Bilateral homonymous hemianopic scotomas secondary to bilateral occipital tip strokes Pseudo-bitemporal defects Incidental field defect What is the next step in this patient’s evaluation? Based on the new interpretation of this patient’s visual field defect, what feature of the examination should be reconsidered? Diagnosis: Tilted disc syndrome Abnormal fields and temporal disc pallor Diagnosis: Dominant optic atrophy Abnormal field and photopsias What aspect of this patient’s visual field defect is atypical for chiasmal compression and suggests instead an ocular disorder? Diagnosis: Rod-cone dystrophy FURTHER READING Visual field testing Tilted disc syndrome Dominant optic atrophy 9 Neuro-ophthalmic look-alikes Idiopathic optic neuritis vs. Leber's hereditary optic neuropathy Based on this patient’s clinical presentation, what is your first diagnostic consideration? Does his clinical course change your mind about the diagnosis? Was there a “red flag” at the time of his initial presentation? Acute tonic pupil vs. pharmacologic mydriasis What commonmechanisms of injury could explain this patient’s pupillary dysfunction? What examination finding can distinguish pharmacologic blockade from postganglionic denervation of the iris sphincter? Chronic tonic pupils vs. Argyll Robertson pupils Is there a physical finding that can differentiate chronic Adie’s pupils from Argyll Robertson pupils? Convergence spasm vs. bilateral sixth nerve palsies What clinical findings would support a diagnosis of convergence spasm? Wernicke's encephalopathy vs. brainstem stroke What aspect of this casemakes an acute brainstem stroke unlikely? What metabolic abnormality can produce this clinical picture? Chronic progressive external ophthalmoplegia vs. progressive supranuclear palsy This combination of horizontal and vertical gaze limitation with slowed saccades could be due to either supranuclear gaze palsy or ocular myopathy. How can we distinguish these two mechanisms? Orbital myositis vs. sixth nerve palsy This patient’s right abduction deficit suggested a sixth nerve palsy. What othermechanism might be responsible and what clinical features suggest this alternative cause? FURTHER READING Optic neuritis vs. Leber’s hereditary optic neuropathy Acute unilateral mydriasis Light near dissociation Convergence spasm Wernicke’s encephalopathy Progressive supranuclear palsy Sixth nerve palsy vs. orbital myositis 10 Over-reliance on negative test results Unexplained visual loss In the absence of any objective abnormalities, would you consider that thismight be non-organic visual loss, perhaps due to job-related stress? Visual loss due to nutritional deficiency was suspected based on hermacrocytosis, however her serum B12 level was within the normal range. What would you like to do next? Diagnosis: Pernicious anemia with normal serum B12 level Twinkling after embolic stroke Now we understand the basis of this patient’s visual field defect. But what is causing her persistent photopsias? Diagnosis: Digoxin toxicity with therapeutic levels Painless ptosis and diplopia Diagnosis: Ocularmyasthenia Headache and third nerve palsy Which diagnostic possibilities should be addressed first? What additional test should be obtained? Diagnosis: Aneurysmal third nerve palsy Truly negative neuro-imaging Brainstem syndrome with negative scan Can you localize this patient’s lesion? What is the most likely etiology in this patient and how would you proceed with the evaluation? Diagnosis: One-and-a-half syndromesecondary to a clinically isolated demyelinating event Homonymous hemianopia with negative neuro-imaging What disease processes would you consider here? Diagnosis: Creutzfeldt–Jakob disease (Heidenhain variant) Non-dominant parietal lobe syndrome with negative neuro-imaging Can you localize this patient’s problem? Diagnosis: Visual variant of Alzheimer’s disease Progressive third nerve palsy What other investigations might be helpful? Diagnosis: Third nerve palsy secondary to nasopharyngeal carcinoma Upgaze palsy What do youmake of this patient’s negative neuro-imaging in light of her clinical presentation? Diagnosis: Shunt malfunction in the absence of ventriculomegaly FURTHER READING Vitamin B12 deficiency Digoxin toxicity Myasthenia Aneurysmal third nerve palsy One-and-a-half syndrome Cortical visual loss with negative neuro-imaging Skull base tumors with negative imaging Shunt failure with negative neuro-imaging 11 Over-ordering tests Isolated unilateral mydriasis This patient’s acute unilateralmydriasis raised the possibility of third nerve palsy due to a posterior communicating artery aneurysm, and the work-up was directed with this possibility in mind. Can isolated mydriasis, in fact, be a sign of a posterior… If an isolated, enlarged and poorly reactive pupil is not a sign of a pCOM aneurysm, what other causes should be considered? Diagnosis: Adie’s tonic pupil Acute unilateral visual loss with disc edema Can you diagnose the cause of this patient’s acute monocular visual loss based on the clinical findings? Are ancillary tests needed? Diagnosis: Non-arteritic anterior ischemic optic neuropathy (NAION) Acute isolated sixth nerve palsy What is the most likely diagnosis and what evaluation would be appropriate? Diagnosis: Vasculopathic cranial mononeuropathy Episodic scintillating scotoma Does this patient need neuro-imaging? An EEG? Other investigation? Diagnosis: Migraine aura Unexplained visual loss What feature in this case suggests nonorganic visual loss? Is additional ancillary testing needed? Diagnosis: Non-organic visual loss FURTHER READING Adie’s tonic pupil Non-arteritic anterior ischemic optic neuropathy Vasculopathic cranial mononeuropathy Migraine Non-organic visual loss 12 Management misadventures Management of idiopathic intracranial hypertension Evaluation and treatment of giant cell arteritis Overzealous treatment of blood pressure in NAION Prednisone for demyelinating optic neuritis Over-reliance on pyridostigmine bromide (Mestinon) in ocular myasthenias Failure to provide symptomatic treatment FURTHER READING Idiopathic intracranial hypertension Giant cell arteritis Non-arteritic anterior ischemic optic neuropathy Optic neuritis Ocular myasthenia Nystagmus Index