Disorders of eye movement: trochlear and abducens palsy, internuclear ophthalmoplegia, and nystagmus

Third nerve palsy is dysfunction of the oculomotor nerve producing ptosis, a down-and-out eye, and often a dilated pupil; a non-pupil-sparing or painful presentation is a posterior communicating artery aneurysm until emergent CT or MR angiography and neurosurgical evaluation prove otherwise, while pupil-sparing cases are managed with vascular risk-factor control.

Multiple sclerosis is an autoimmune, demyelinating CNS disorder causing optic neuritis, myelitis, and brainstem/cerebellar syndromes separated in space and time. Diagnosis uses the McDonald MRI-based criteria; acute relapses are treated with high-dose glucocorticoids, and disease-modifying therapy (interferon beta, glatiramer, or a higher-efficacy agent such as ocrelizumab or natalizumab) is started early to prevent relapse and disability accumulation.

Ischemic stroke is sudden focal neurologic deficit from arterial occlusion confirmed by infarction on neuroimaging. Diagnosis relies on urgent noncontrast head CT to exclude hemorrhage; treatment is IV alteplase within 4.5 hours and mechanical thrombectomy for large-vessel occlusion within an extended window, followed by antiplatelet therapy and risk-factor control.

Cerebellar stroke, ischemic or hemorrhagic infarction of the cerebellum, presents with vertigo, truncal ataxia, dysarthria, and limb incoordination and is diagnosed with brain MRI when CT is falsely reassuring. Its defining danger is delayed swelling that compresses the brainstem and fourth ventricle, which is treated with emergent decompressive suboccipital craniectomy.

Horner syndrome is an oculosympathetic palsy causing the ipsilateral triad of miosis, partial ptosis, and anhidrosis from a lesion anywhere along the three-neuron sympathetic pathway to the eye and face. Diagnosis is clinical, confirmed with apraclonidine or cocaine eye drops; management targets the underlying cause, which ranges from benign to an emergent carotid dissection or Pancoast tumor.

Myasthenia gravis is an autoimmune disorder of the postsynaptic neuromuscular junction, most often caused by acetylcholine receptor antibodies, producing fluctuating, fatigable weakness of ocular, bulbar, and limb muscles. Diagnosis rests on antibody testing and electrodiagnostics; first-line treatment is pyridostigmine, with glucocorticoids and steroid-sparing immunosuppression for generalized disease and thymectomy for eligible patients.

Idiopathic intracranial hypertension (formerly pseudotumor cerebri) is raised intracranial pressure of unclear cause, without a mass lesion or hydrocephalus, occurring mainly in obese women of childbearing age and presenting with headache, papilledema, and visual symptoms. Diagnosis requires an elevated lumbar puncture opening pressure with normal CSF and normal or empty-sella imaging; treatment centers on weight loss and acetazolamide to protect vision, with surgery reserved for medically refractory disease.

Sustained intracranial pressure above 20-22 mmHg from mass effect, edema, hydrocephalus, or venous outflow obstruction, diagnosed by clinical signs plus invasive monitoring and treated stepwise with head elevation, hyperosmolar therapy (mannitol or hypertonic saline), CSF diversion, and decompressive surgery when refractory.

Papilledema is bilateral optic disc swelling from raised intracranial pressure, most classically idiopathic intracranial hypertension; imaging to exclude a mass lesion or venous sinus thrombosis must precede lumbar puncture, and acetazolamide is the first-line drug once idiopathic intracranial hypertension is confirmed.

Septic thrombosis of the cavernous sinus from spreading facial, sinus, or orbital infection, marked by fever, proptosis, chemosis, and cranial nerve palsies that classically become bilateral. It is a neuro-ophthalmic emergency treated with immediate broad-spectrum IV antibiotics, source control, and consideration of anticoagulation.

BPPV is the most common cause of vertigo, produced by displaced otoconia in a semicircular canal, most often the posterior canal, and is diagnosed at the bedside with the Dix-Hallpike maneuver and treated first-line with the canalith repositioning (Epley) maneuver rather than medication.

Vestibular neuritis and labyrinthitis are presumed viral or post-viral inflammatory disorders of the vestibular nerve or labyrinth causing sudden-onset, continuous vertigo lasting days, with labyrinthitis distinguished by added cochlear symptoms of hearing loss and tinnitus. The essential diagnostic task is excluding a posterior-circulation stroke at the bedside using the HINTS exam before treating with short-course vestibular suppressants, early corticosteroids, and vestibular rehabilitation.

Graves disease is an autoimmune disorder in which thyrotropin receptor antibodies stimulate the thyroid, causing hyperthyroidism, and is the most common cause of thyrotoxicosis in iodine-sufficient regions. Diagnosis rests on a suppressed thyroid-stimulating hormone with elevated free thyroxine and positive thyrotropin receptor antibodies, and first-line treatment is a thionamide, most often methimazole, with radioactive iodine or thyroidectomy reserved for recurrence or patient preference.