This is a UKMLA-centred history guide about limb weakness.

Introduction

Limb weakness can be categorised as functional, such as conversion syndrome, or pathological, due to muscle weakness, which can be primary, such as myositis, myopathy muscular dystrophy, or secondary, due to neuronal death, neuronal dysfunction and peripheral vascular disease.

Total muscle weakness, i.e. MRC rating of 0/5, is defined as paralysis and words end in “-plegia” e.g. hemiplegia, whereas partial muscle weakness is called paresis, which is much more common.

UMN vs LMN Signs

When considering a neurological cause of limb weakness, it is important to distinguish between an upper motor neuron (UMN) lesion or lower motor neuron (LMN) lesion.

Typical Histories of Common OSCE Conditions

UMN Condition

LMN Condition

Mixed UMN and LMN Condition

Presenting Complaint

Site

Unilateral weakness e.g. stroke, plexus lesions such as Erb’s palsy

Bilateral weakness

• Autoimmune – myasthenia gravis, Lambert-Eaton syndrome, Guillain Barre syndrome, multiple sclerosis
• Cord compression – syringomyelia, degenerative cervical myelopathy
• Idiopathic – motor neuron disease
• Proximal predominance – polymyositis, Cushing’s disease, steroid-induced myopathy, statin-induced myopathy, muscular dystrophy, polymyalgia rheumatica
• Distal predominance – peripheral neuropathy such as diabetic neuropathy, mononeuritis multiplex or peripheral vascular disease

Dermatomal distribution e.g. nerve root compression causing radiculopathies

Onset

Early childhood/adolescence – muscular dystrophy, multiple sclerosis

Late adulthood – motor neuron disease (>60 years), stroke

Character

Shooting pain radiating down the leg – sciatica 

Dull pain – spinal stenosis

Timing

Sudden onset:

• Trauma
• Ischaemic or haemorrhagic stroke
• Infection e.g. Guillain Barre syndrome
• Malignancy e.g. metastatic spinal cord cord compression

Gradual and progressive:

• Infection e.g. cerebral abscess
• Neurodegeneration e.g. MND, multiple sclerosis (MS)
• Malignancy e.g. growing tumour

Relapsing-remitting e.g. MS

Associated Symptoms

Back pain e.g. cauda equina syndrome, spinal stenosis, sciatica

Back pain and fever e.g. discitis, spinal abscess

Weakness with no sensory deficits e.g. MND

Precipitating Factors

Pain is worse walking downhill and improves bending forward → spinal stenosis

Viral/bacterial infection specifically Campylobacter → GBS

Difficult delivery (e.g. shoulder dystocia), swinging child by arms → Klumpke’s/Erb’s palsy

Red Flags

Bladder or bowel dysfunction e.g. cauda equina syndrome

Acute, focal neurological deficits e.g. stroke

Nocturnal headache, headache worse on lying down e.g. space-occupying lesion

Progressive weakness e.g. CNS tumour, MND, MS

Worsening back or thoracic pain e.g. spinal cord metastases

Fever, night sweats, rigors e.g. epidural abscess

Background

In any history you will ask about past medical history, medications, allergies, social history, and family history. In a history around fever in children, you can show how much you know about the various causes by explicitly asking about the following things:

Past Medical History

Diabetes → diabetic neuropathy

Malignancy → spinal cord or brain metastases

Thrombophilia → ischaemic stroke

Steroid use/statin use → proximal myopathy

Autoimmune disease e.g. type 1 diabetes → myasthenia gravis, multiple sclerosis

Family History

Charcot-Marie-Tooth disease

Friedreich’s ataxia

Social History

Recreational drug use e.g. nitrous oxide → subacute combined degeneration of spinal cord

IV drug use → discitis, epidural or brain abscess

Alcohol misuses → alcohol neuropathy, B12 deficiency

Significant history of smoking tobacco → Lambert-Eaton syndrome

Examination of Limb Weakness

Have a set of differentials prior to examining so you can rule in or out depending on the signs you elicit. Remember common is common! The aim of OSCE’s to assess your ability to identify common conditions and practice as a safe doctor e.g. not sending someone home if your suspect spinal cord compression.

Inspection

• Consider their age and gender and observe their gait and how they stand up from sitting. 
• Look for fasciculations and muscle atrophy. The presence suggests a LMN lesion.
• For example, an elderly man with unilateral fixed flexion of the upper limb and fixed extension of the lower limb with circumduction is highly suggestive of stroke.
• If the person has difficulty standing up from a sitting position, it is suggestive of proximal muscle weakness.

Palpation

• Assess tone, power and reflexes for motor neuron function
• Consider the differential stated above depending on the signs elicited
• Assess sensory modalities e.g. pin-prick, crude touch, vibration and proprioception
• A sensorimotor deficit suggests multiple nerves are affected e.g. radiculopathies, peripheral neuropathies, mononeuritis multiplex, multiple sclerosis, etc

References
 
1. Hamed Khan et al. OSCE’s for medical finals
2. Davidson’s Principles and Practice of Medicine, 24th Edition

Author – Dr Karthikeyan Sivaganesh 

Editor – Dr James Mackintosh

Last updated 05/05/24