Excessively tired and Sleepy
A 48-year-old man presents to his GP feeling excessively tired for the last few months. He reports that he often falls asleep at work and is unable to concentrate. He denies any other constitutional symptoms or weight loss.
Past Medical History:
Q1: Comment on the blood results – what is the likely cause of his tiredness?
Q2: Why is he more at risk of developing this condition?
He is offered medication to treat the condition but is often forgetful and fails to take the medication regularly. 10 years later he is brought to A&E by his wife as she noticed he was dragging both his feet on the floor.
Speech: Fluent, meaningful
Pupils: Symmetrical and reactive to light
Cranial nerves: NAD
Upper limb: NAD, normal power, reflexes, and sensation
Lower limbs: Increased tone, brisk knee reflex but absent ankle reflex bilaterally
Bilateral high steppage and stomping gait
Loss of sensation and vibration bilaterally
Q3: Account for the neurological findings – what complication has developed?
Q4: What are the differential diagnoses for his presentation to A&E?
He has a megaloblastic anaemia (high MCV), thus the likely differentials are B9/12 deficiency, alcoholism, Haemolytic anaemias and myeloproliferative disorders.
Normal electrolytes suggest that an endocrine disturbance e.g. Addisons or Cushing’s secondary to his steroid prescription is unlikely to be the cause.
Normal thyroid tests exclude hypothyroidism.
Elevated methylmalonic acid and homocysteine give a diagnosis of B12 (Cobalamin) deficiency – B12 is a co factor in the conversion of homocysteine + folate to methionine and methyl malonyl CoA to succinyl-CoA (if there was an isolated folate deficiency only homocysteine would be elevated).
He has Crohn’s disease, which often affects the terminal ileum – this is the site of B12 absorption in the GI tract.
Normal speech and upper limbs excludes and brain or C spine pathology
Hyperreflexia and hypertonia in LL suggest thoracic cord pathology with damage to primary corticospinal neurons in the lateral aspect of the cord (lumbar spinal pathology would give LMN lesions as the cord ends at L1)
An interesting finding in this patient is the presence of LMN lesions of the ankle – this is due to a superimposed peripheral neuropathy
The high steppage gait indicates weakness of the foot dorsiflexors and the stamping gait suggests a lack of proprioceptive input into the cord – damage to the posterior dorsal columns
Overall, this is in keeping with subacute degeneration of the spinal cord – this can occur in patients with longstanding B12 deficiency – as such it is vital that folate levels are checked at the same time as B12 and that in patients with mixed deficiency B12 is corrected FIRST
The differential diagnosis for ‘mixed’ UMN and LMN signs in the same limb include:
– Fredreich’s Ataxia
– Subacute degeneration of the cord
– Tabes dorsalis
– Amyotrophic lateral sclerosis (no sensory symptoms)
– Progressive bulbar palsy (no sensory symptoms)
To get more information about the conditions mentioned in this case including diagnosis and management, have a look at our free haematology notes on In2Med. Written by medical students, we have pitched them just at the right level to help you ace your exams.