• Ipsilateral (same side):
o Weakness (UMN signs below lesion: spasticity, hyperreflexia).
o Loss of vibration and proprioception (dorsal column).
• Contralateral (opposite side):
o Loss of pain and temperature sensation (spinothalamic tract, crossing at entry level).
• Causes:
o Trauma (e.g., stab wound).
o Spinal tumors.
o Demyelination (MS).
• Amyotrophic Lateral Sclerosis (ALS) = most common subtype.
• Key features:
o Mixed UMN (spasticity, brisk reflexes, upgoing plantars) and LMN (wasting, fasciculations, weakness) signs.
o No sensory symptoms.
o Often affects limbs asymmetrically → "split hand sign" (wasting of lateral hand muscles with sparing of medial).
• Bulbar signs:
o Dysarthria, dysphagia, tongue fasciculations.
o "Pseudobulbar affect" (emotional lability).
• Respiratory involvement:
o Weakness → respiratory failure is common terminal event.
• Treatment:
o Riluzole (glutamate inhibitor) → modestly prolongs survival (~3 months).
o Symptomatic support (non-invasive ventilation improves survival and QoL).
• Variants:
o Progressive muscular atrophy (pure LMN).
o Primary lateral sclerosis (pure UMN).
o Progressive bulbar palsy.
• Suggests mixed UMN and LMN pathology, classic in:
o MND.
o Subacute combined degeneration (if also B12 deficiency, but would have sensory loss).
• Motor loss below lesion:
o Bilateral weakness (corticospinal tract).
• Loss of pain and temperature below lesion:
o Spinothalamic tract involvement.
• Sparing of vibration and proprioception:
o Dorsal columns supplied by posterior spinal arteries.
• Common causes:
o Aortic dissection.
o Severe hypotension.
o Vasculitis.
• Rare.
• Loss of vibration and proprioception below lesion.
• Motor and pain/temp usually spared.
Extra Revision Pearls
• ALS clue: "No sensory loss despite severe weakness → think MND."
• Bulbar vs pseudobulbar:
o Bulbar (LMN): tongue wasting, fasciculations.
o Pseudobulbar (UMN): spastic tongue, brisk jaw jerk, emotional lability.
• Brown-Séquard clue: "Crossed sensory findings + unilateral weakness."
• Anterior spinal artery infarct clue: "Can't move or feel pain/temp below lesion, but still sense vibration."
• "Split hand sign" in ALS: selective atrophy of lateral hand muscles (thenar, first dorsal interosseous).
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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.
