Delve into the neuro Ddx with expert diagnosticians the @CPSolvers, Drs. Reza Manesh (@DxRxEdu) and Rabih Geha (@rabihmgeha). Play along as they solve a neurology mystery case, and give us a tour of the neuraxis.
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70F with h/o diabetes presents with a fall. She had several months of progressive bilateral lower extremity (LE) weakness, along with proximal muscle weakness of the upper extremities (UE). On exam we detect ptosis, bifacial weakness, and hyporeflexia.
Weakness Thought Train on CPSolvers site
CPSolvers schema on bilateral LE weakness https://clinicalproblemsolving.com/dx-schema-bilateral-lower-extremity-weakness/.
Localize the lesion to the brain, spinal cord, cauda equina, peripheral nerve, NM junction, or muscle. Often we assume a single “elegant lesion” that explains all neurologic symptoms. BUT, don’t forget to consider multiple lesions! Neurologist, Dr. Aaron Berkowitz, recommends that we localize the lesion, and then consider the time course to prioritize the differential diagnosis (Ddx).
Upper Motor Neuron (UMN) lesions usually cause hyperreflexia, spasticity, and upgoing toes. But, in the acute setting patients may have hyporeflexia.
Miller-Fisher Variant of Guillain-Barre: Acute onset of ataxia, hyporeflexia and ophthalmoplegia (Check out the NIH-NINDS summary).
Brain lesions often have cognitive symptoms along with bowel or bladder dysfunction.
Guillain-Barre – usually lacks bowel and bladder symptoms, which can differentiate it from other causes of bilateral weakness.
Usually due to MYOPATHY. ALS can initially present similar to inclusion body myositis as can a plexopathy (e.g. sometimes seen in diabetes). An elevated CK or statin use can point us to myopathy. Hyporeflexia is usually absent with myopathy unless it is very advanced.
Are you seeing a disorder with features of nerve and muscle involvement (e.g. proximal muscle weakness and hyporeflexia)? Consider an NMJ (neuromuscular junction) lesion.
Further break it down to:
*Ptosis, plus a spared pupil? Think Myasthenia Gravis.
Ice pack test (Sethi Neurology 1987): Place ice pack on the patient’s eyelid. This causes increased acetylcholine and the ptosis will improve in Myasthenia Gravis.
Split this into inflammatory vs non-inflammatory causes.
Inflammatory: Infection, Malignancy, Autoimmune
Non-inflammatory: Muscle weakness, Cognitive dysfunction, Malabsorption, etc.
1. Infection: Cavitary lesions, Abscess, Tuberculosis, Fungal “omas”
2. Inflammatory: Sarcoidosis, GPA, Rheumatoid Nodules
3. Malignancy: Metastatic lesions, Carcinoid, Small Cell Lung Cancer, Non-small Cell Lung Cancer
Reza’s NSCLC mnemonic = “A SAD Lung” – adenocarcinoma [peripheral], squamous [central], large cell [peripheral].
A paraneoplastic syndrome of the presynaptic neuromuscular junction caused by an auto-antibody against Voltage gated Calcium channels (VGCC). Small cell lung cancer is a frequent association. Clinical symptoms include proximal muscle weakness, hyporeflexia, and sensory symptoms. Ptosis can also be seen. On EMG there is reduced amplitude of the compound muscle action potentials, and improvement with repetitive stimulation (Kesner Neurol Clin 2018).
Reflect on performance to improve your skills for the future. For this case, Rabih points out that a neurologist’s neuro exam is superior and often required to pick up subtleties that might be missed by a less experienced clinician. Reza reminds us that the neuro Ddx is dependent upon localization and the time course of symptoms.
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Listeners will practice their clinical reasoning skills as they pertain to this neurology mystery case.
After listening to this episode listeners will…
Drs. Manesh and Geha report no relevant financial disclosures. The Curbsiders report no relevant financial disclosures.
Minter D, Manesh R, Geha R, Williams PN, Watto MF. “#278 Neuro Mystery Case with The CPSolvers”. The Curbsiders Internal Medicine Podcast. http://thecurbsiders.com/episode-list Final publishing date June 7, 2021.
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