Today, we discussed the case of an elderly woman with significant malignancy history who presented with acute kidney injury and a constellation of neurologic symptoms/findings including gait instability, dysarthria, vertical nystagmus, asterixis, and visual hallucinations. A diagnostic mystery, but a fascinating case to think about the differential diagnosis, which included paraneoplastic neurologic syndromes!
A Plug for Paraneoplastic Neurologic Syndromes!
See our prior blog post on paraneoplastic neurologic syndromes: https://ucsfmed.wordpress.com/2016/06/17/moffitt-oncology-report-pearls-61716-paraneoplastic-neurologic-syndromes-and-hyperammonemia/
Differentiating Central versus Peripheral Nystagmus
- Symptoms: Peripheral nystagmus is often associated with severe vertigo and vomiting; symptoms of central nystagmus range widely from none to pronounced vertigo.
- Time-course: peripheral nystagmus almost always remits within a few days to weeks (due to central adaptive mechanisms and development of ability to suppress nystagmus with visual fixation)
- Waveform: Pure downbeat, pure upbeat, or pure torsional nystagmus are almost always central brainstem signs : pure horizontal or mixed forms are typical of peripheral causes of nystagmus
Different Types of Nystagmus
- Horizontal Nystagmus (Peripheral or Central)
- May be peripheral or central
- Peripheral: usually due to unilateral loss of labyrinthine input from vestibular neuritis or partial neurectomy : BPPV is due to hyperfunction of the semicircular canal (due to canalithiasis)
- Central: Think various lesions affecting cerebrum or vestibular nuclei : Wernicke encephalopathy
- Upbeat Nystagmus (Central)
- Most commonly affected lesion is the medulla
- Most frequent causes: cerebellar degeneration and brainstem/cerebellar stroke
- Unusual causes: viral encephalitis, meningitis, sarcoidosis, Behcet’s syndrome, anti-GAD antibodies.
- Downbeat Nystagmus (Central)
- usually due to damage to dorsal medulla or cerebellar flocculus
- Most frequent causes include Chiari malformation, cerebellar degenerations, MS, vertebrobasilar infarction, medications, alcohol
- Torsional Nystagmus (Central)
- Central nystagmus due to dysfunction of vertical semicircular canal inputs from one side; lesions are at lateral junction of pons and medulla that involve the vestibular nuclei
- Causes: infarction and multiple sclerosis are most common : Tumors and venous angiomata in pons or cerebellum are the next most frequent causes.