Survival Guide

Building a neurological differential 🧩

Tempo plus localisation gives you the syndrome; syndrome plus context gives you the differential.

Neurology is terrible because one complaint (“I can’t walk properly”) can come from a whole bunch of different places, and a whole bunch of different diseases. This is however the reason that neurology is actually great. You’ve just gotta lean in and break things down: Stop jumping from complaint to diagnosis and break things down into the syndrome instead. Once you start with a syndrome and move out everything starts to make sense, and it stops feeling like you’re just doing the same 3 tests on every patient (although don’t worry! You’ll get to do that sometimes too).

Why bother? 🤔

Neurology is about being systematic because it allows you to get a grip on what can otherwise be a bit overwhelming. Breaking things down like this allows you to:

• boil any presentation (no matter how bizarre) down to its core so you can find out what’s going on
• order fewer scans, and fewer wrong scans
• stop chasing your tail interpreting lots of slightly abnormal tests
• know how much examination this particular patient actually needs
• keep a running list of the bits that don’t fit, so you can come back to them when the illness evolves

Doing this dance is a skill that is you can work on for a whole career, and is one of the reasons that neurology is so good. Trust me.

Step 1: Tempo ⏱️

Tempo is how the symptoms started and evolved

The categories blur into each other a bit. What matters is you can tease it out when needed:

• Hyperacute: the patient or family can tell you exactly where they were and what they were doing. There is a sharp line between normal and not.
• Acute: the baseline is still clear, but the exact onset is usually a bit fuzzy. “He had a fever last night, a headache this morning, and by this evening he wasn’t making sense.”
• Subacute: the beginning of symptoms is blurrier. You often need to anchor questions to events: “Were you like this at your daughter’s birthday?”, Patients often remember the first time it mattered (the trip on the kerb) rather than when it started.
• Chronic: there may be no start at all, only a time in the past when the family is sure things were fine.

Step 2: Localisation 📍

Localisation is working out where the lesion is. Most of your localisation comes from history, not examination. We’ll go into this in more detail in the next chapter so don’t stress. You’ll be glad to know that there’s whole textbooks written on this stuff, and again you can choose to spend a whole career refining this.

In a nut-shell though: Work from the top down and drill as deep as you can:

1. Central or peripheral?
2. Central: cerebral hemisphere (cortex, subcortical white matter, basal ganglia, thalamus), brainstem (midbrain, pons, medulla), cerebellum, or spinal cord (which tracts, which level)?
3. Peripheral: root, dorsal root ganglion, plexus, nerve (axon or myelin), neuromuscular junction (pre- or post-synaptic), or muscle (proximal or distal)?

The localisation chapter has the patterns.

Step 3: Tempo + localisation = syndrome 🧠

The syndrome is your clinical assessment: “an acute, rapidly progressive cervical myelopathy”, or “a chronic length-dependent sensorimotor neuropathy”.

Step 4: Syndrome + context = differential 🗂️

Context is the rest of the history: past medical and surgical history, drugs, family, social history, etc. You need to reason out what is relevant. Context orders the differential, but rarely removes anything from it (e.g patients with HIV get opportunistic infections, but the white matter hyperintensity could still be MS).

Presenting a neurological case 🎤

You can use the above scaffold to structure a case presentation. The level of detail should be tailored to the acuity of the case

1. The one-liner. Age, highly relevant context, syndrome. “A 62-year-old man with AF who isn’t anticoagulated, with a hyperacute L hemispheric syndrome starting 90 minutes ago, NIHSS is 20”; or “a 40-year-old lady with a background of MS who self-ceased ofatumumab 2 years ago, presenting with acute apparent left eye optic neuritis” If you say nothing else, this is the sentence that matters.
2. The story/tempo. Onset, evolution, and what has happened since. Then the associated symptoms, and the pertinent negatives: the ones that would have changed the localisation (no headache, no neck pain, no seizure, no sensory symptoms).
3. Context. Past history, drugs, family, social. Only the parts that order the differential, and say why you’re mentioning them (“on apixaban, last dose last night”, “smoker”, “mum had MS”).
4. Examination. Positives first, then the negatives that matter, grouped by level: mental state and language, cranial nerves, limbs, gait. “Cranial nerves intact” is not a finding. “Fields full, no facial weakness, no dysarthria” is.
5. Syndrome. Summarise by repeating the syndrome
6. Differential. Most likely first, then the can’t-miss, ordered by the context. Two or three things, not ten.
7. Plan. What you’re going to do: Disposition, tests, treatment, referrals.

Adapted and condensed from Chapter 1 of How to Think Like a Neurologist (Ethan Meltzer, Oxford University Press), which builds on Berkowitz’s Clinical Neurology and Neuroanatomy and Adams and Victor’s Principles of Neurology.