• Bacterial meningitis:
o Appearance: cloudy/turbid.
o Cells: high neutrophils (polymorphs).
o Protein: elevated (>1 g/L).
o Glucose: low (<50% of plasma glucose).
o Opening pressure: often high.
• Viral meningitis:
o Appearance: clear.
o Cells: lymphocytic predominance.
o Protein: mildly elevated or normal.
o Glucose: normal.
• Tuberculous meningitis:
o Lymphocytes, very high protein, very low glucose.
o "Cobweb" formation on standing.
• Fungal (e.g., cryptococcus):
o Common in immunosuppressed.
o Lymphocytes, low glucose, high opening pressure.
• Multiple sclerosis:
o Oligoclonal bands: present in CSF but absent in serum (indicates intrathecal synthesis).
• Subarachnoid haemorrhage:
o Xanthochromia (bilirubin breakdown product), persists >12 hours.
• CT head:
o Indications: acute stroke (to exclude bleed), head trauma, hydrocephalus.
o Early detection of haemorrhage (hyperdense), late detection of infarct (hypodense).
o Better for bone detail.
• MRI brain:
o Demyelinating lesions (MS plaques), tumours, posterior fossa structures, encephalitis (temporal lobes in HSV).
o DWI sequence for early ischaemia.
• MR angiography/CT angiography:
o Vessel occlusion or aneurysms (e.g., SAH work-up).
• Nerve Conduction Studies (NCS):
o Differentiate axonal loss (reduced amplitude) vs demyelination (slowed conduction velocity, prolonged distal latencies).
• Electromyography (EMG):
o Muscle diseases (myopathic changes: small, polyphasic units).
o Neurogenic changes: large, polyphasic units with reduced recruitment.
• Repetitive nerve stimulation:
o MG: decremental response.
o LEMS: incremental response with high-frequency stimulation.
• Single-fibre EMG:
o Most sensitive for MG.
• Used for:
o Epilepsy diagnosis (generalised spike-wave discharges in absence seizures).
o Encephalopathies (triphasic waves in metabolic encephalopathy).
o Brain death assessment (absence of activity).
• Visual Evoked Potentials (VEP):
o Delayed P100 latency → optic neuritis (early demyelination marker).
• Somatosensory Evoked Potentials (SSEP):
o Assess dorsal column function; useful in MS and spinal cord disease.
• Brainstem Auditory Evoked Potentials (BAEP):
o Diagnose acoustic neuromas, brainstem lesions.
Extra Revision Pearls
• Always check for raised ICP before LP → risk of coning.
• MRI is superior for posterior fossa and spinal cord.
• Oligoclonal bands in CSF but not serum = strong clue for MS.
• EMG/NCS patterns help differentiate neuropathy (length-dependent, "glove and stocking") vs myopathy (proximal weakness).
• EEG can be normal between seizures → does not exclude epilepsy.
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Author & Educational Disclaimer
Author:
Dr Phillip Cockrell BM FRCP DipClinEd
Dr Phillip Cockrell is a UK Consultant Physician in Internal Medicine, currently working at Queen Alexandra Hospital, Portsmouth University Hospitals NHS Trust. He has previously worked as a registrar across Intensive Care Medicine, Gastroenterology, Cardiology, Stroke Medicine, Acute Medicine, and Respiratory Medicine.
He has held senior leadership roles including Associate Clinical Director of the Acute Medical Unit, Clinical Director of Internal Medicine, and Chief of Medicine. Dr Cockrell has over 15 years’ experience in postgraduate medical education, having lectured extensively across the MRCP syllabus and contributed to MRCP revision teaching and course development.
Dr Cockrell holds a Bachelor of Medicine (BM), Fellowship of the Royal College of Physicians (FRCP), and a Diploma in Clinical Education (DipClinEd). His teaching approach is based on structured consolidation of complex medical topics to support efficient and effective revision for postgraduate examinations.
Purpose of this content:
The material on this page is intended solely for educational purposes to support revision for the MRCP (UK) Part 1 examination. It reflects examination-relevant principles of internal medicine and is designed to aid learning and pattern recognition.
Medical disclaimer:
This content is designed for postgraduate medical examination revision and does not constitute medical advice, diagnosis, or treatment guidance and must not be used as a substitute for professional clinical judgement, local guidelines, or specialist consultation. Clinical decisions should always be made in the context of individual patient circumstances and current national guidance.
