Limb Weakness Station

Presenting Complaint

• You are worried as you have been tripping involuntarily while walking your dog.

History of Presenting Complaint

• Site: Difficulty lifting both legs on walking but predominantly on the left. Wife feels that you lift your legs much higher than usual when walking

• Onset: First tripped 3 months ago. 

• Character: Legs feel weak and heavy

• Timing: Last week tripped 3 times on different days. It has worsened since onset (Student must specifically ask if symptoms have worsened).

• Associated features: No sensory changes (only if specifically asked), no joint pain, no pain in legs or back. Sometimes, have difficulty holding the cup of tea and once dropped it accidentally.

• Exacerbating/Relieving factors: No provoking factors. Tripping happens unexpectedly. You sit more often, but this does not help.

Systems Review

• Neurological: apart from leg weakness, no other neurological deficits
• GI: No change in bladder or bowel function
• Otherwise well, no other problems
• Red flags: as below
  • Trousers feel looser around the calf and thigh.
  • Feel more tired recently but no night sweats, change in appetite, fevers or recent infection

Previous Medical History

• Well controlled Asthma
• No known hospital admissions or recent surgeries

Drug History

• Blue Salbutamol inhaler PRN

Allergies

• NKDA

Social History

• Stopped smoking 5 years ago - smoked 5 a day for 20 years (only if asked).
• Drink alcohol on social occasions only.
• Never taken recreational drugs.
• Works as a chef at a renowned restaurant.
• Live with your wife with no problems at home.

Family History

• Father has Parkinson's Disease
• Mother has Breast Cancer

ICE

• Ideas: Thinks this might be Parkinson’s disease
• Concerns: Worried about Parkinson’s and if symptoms will impact your ability to work
• Expectations: Want to know the diagnosis and if you should do anything to improve the symptoms.

Vitals

• HR: 76 bpm
• BP: 126/84 mmHg
• SpO₂: 98%
• Temperature: 36.6℃
• Respiratory Rate: 14 breaths per min

Neurological Examination

• Upper limbs: 
  • Mild atrophy of thenar eminence. 
  • Normal tone. 
  • Normal power on all joint movements. 
  • Reflexes normal. 
  • Pin-prick, vibration and proprioception sensation normal.
• Lower limbs: 
  • Prominent atrophy of tibialis anterior in the left leg compared to the right. Fasiculations are seen bilaterally.
  • Reduced tone bilaterally.
  • Reduced power on dorsiflexion of both feet but prominent on the left. Reduced power on hip flexion bilaterally but normal power in other joint movements.
  • Increased reflexes on tapping the patellar and Achilles tendon. Babinski's sign is negative bilaterally.
  • Pin-prick, vibration and proprioception sensation normal.

1. What is the most likely diagnosis and explain why?

• Motor neuron disease (MND) - a mix of upper and lower motor neuron signs in the absence of sensory deficits is characteristic of MND. A bilateral foot drop suggests a systemic problem rather than a local one. Patients often present with involuntary tripping or difficulty holding objects due to reduced muscle strength

2. What are the types of MND?

• Amyotrophic Lateral Sclerosis (ALS is the commonest type). Subtypes include:
  • Spinal ALS → classic MND
  • Bulbar ALS → Tongue, muscles involved in chewing and swallowing are affected causing difficulty talking, chewing and swallowing
• Progressive Muscular Atrophy – Only lower motor neuron signs. Distal muscles affected before proximal muscles
• Primary Lateral Sclerosis – Only upper motor neuron signs

3. What blood tests would you consider doing in primary care?

• Bloods:
  • Vitamin B12, Folate - to exclude subacute combined degeneration (although unlikely as there are no sensory deficits, it can cause both upper and lower motor neuron signs)
  • FBC and Iron studies - assess for microcytic anaemia, which can cause tiredness. If iron deficient, consider bowel cancer due to patient’s age
  • Thyroid Function Tests - hypothyroidism can cause tiredness

4. Given the suspected diagnosis of MND, how would you manage this patient in primary care?

• Urgent referral to neurologist informing about a suspected diagnosis of MND (as per NICE guidance).
• Provide the patient with a leaflet about the diagnosis and direct them to local support groups or national charities that can help them through their diagnosis.
• Discuss legal rights, including social care support, occupational therapy input, physiotherapy, employment rights and benefits.
• Notify the Driver and Vehicle Licensing Agency (DVLA).
• Opportunities for advance care planning e.g. LPA

5. What treatment may be provided in secondary care?

• Riluzole
  • Glutamate receptor antagonist
  • Prolongs life by about 3 months
• Respiratory care – Use BIPAP (non-invasive ventilation) at night
• Nutrition support – Percutaneous endoscopic gastrostomy tube (PEG) is preferred due to impaired swallow
• Prognosis is poor: 50% of patients die within 3 years of diagnosis