Routine for examination of lower limbs:
Inspect (wheelchair/walking aid/orthotic device, pes cavus)
Gait and Rhombergs
Tone
Power
Reflexes
Coordination
Sensation (prioritise joint position sense and vibration if suspect Friedrich’s ataxia)
If time allows and you suspect Friedreich’s ataxia proceed as follows:
Hands and arms: fingerprick marks (diabetes) and coordination (past pointing, intention tremor, dysdiadochokinesis, rebound)
Eye movements for nystagmus
Mouth (high arched palate) and speech e.g. “How did you get here today?” (dysarthric)
Ears: hearing aid, CN VIII (sensorineural hearing loss)
Chest: feel apex beat, listen to heart sounds, look for pacemaker (hypertrophic cardiomyopathy, conduction defects)
Back: check for kyphoscoliosis
Fundoscopy: optic atrophy
Present to the examiner:
This patient has a spastic paraparesis as evidenced by:
Increased tone
Pyramidal weakness
Upgoing plantars and clonus
The ankle (and knee) reflexes were however absent
There were cerebellar signs such as past pointing, intention tremor, dysdiadochokinesis, rebound, heel-shin ataxia, dysarthria, nystagmus. The patient was unable to walk/had an ataxic/spastic gait and there was a wheelchair/walking aid by the bedside
There were dorsal column signs (loss of vibration and joint position sense).
Rhomberg’s test was positive
I noticed pes cavus, kyphoscoliosis, hearing aid, pacemaker, diabetic fingerprick marks etc.
The combination of spinocerebellar signs, corticospinal tract signs and dorsal column loss is suggestive of Friedrich’s ataxia.
My differential diagnosis is:
- Friedreich’s ataxia
- Demyelination (would expect brisk reflexes)
- Other causes of mixed upper and lower motor neuron signs such as upgoing plantar with absent ankle jerk (subacute combined degeneration of the cord, taboparesis, cervical myelopathy with peripheral neuropathy, motor neuron disease)
- Vitamin E deficiency is a rare mimic of Friedrich’s ataxia
Friedreich’s Ataxia
A progressive neurodegenerative disorder
The most common inherited ataxia in the UK
Onset usually < 20 years old
Autosomal recessive. Frataxin gene on chromosome 9. Trinucleotide repeat (GAA).
Investigations:
Bloods: vitamin E level, glucose/Hba1c, B12, syphilis
Nerve conduction studies: absent/reduced sensory action potentials, increased motor velocity
MRI brain and spinal cord (atrophic changes may be seen)
ECG: LVH, arrhythmia
CXR: cardiomegaly
Echo: to assess for cardiomyopathy
Genetic testing
AMTS/MMSE (mild dementia)
Management:
Multidisciplinary approach (geneticist, physio, OT, neurology, cardiology, orthopaedics, diabetic nurse, orthotics, GP)
Annual neurology, cardiology, musculoskeletal and diabetes check
Manage complications: cardiac, orthopaedic, diabetes
Screen family members
Written by Dr Sarah Kennedy
Resources used to write this document are listed in the references section of this webpage