A list of aetiologies

The college loves to ask the candidates qestions on the tme of "why is this patient having sizures?". These tend to have some list of biochemistry results, or have a highly suggestive history which leads to a broad range of differentials. One example of such a question is Question 21 from the second paper of 2016, where a young woman presents with seizures after a few days of "unusual behaviour".

Why is she fitting? There are numerous reasons for why one might have a seizure, and of these the majority can (by extension of their magnitude) become causes of status epilepticus. Of course, the most common causes are failure to take one’s own epilepsy tablets.  For the weird causes, there is a good article which lists a massive spectrum of toxins, genetic diseases, rare autoimmune conditions and what have you.

Without further ado, here is a list of possible causes.

Vascular causes:

  • Stroke
  • Decreased cerebral blood flow: ischaemic encephalopathy
  • Increased cerebral blood flow: hypertensive encephalopathy
  • Eclampsia falls into this category
  • Intracranial haemorrhage – eg. subarachnoid

Infectious causes:

Encephalitis

  • Meningitis
  • Brain abscess

Neoplastic lesions:

  • Space-occupying tumour

Drug-induced status epilepticus

 

Drug withdrawal:

  • From any sort of depressant, but classically from alcohol benzodiazepines and barbiturates. It is generally believed that one should never cease a barbiturate agent abruptly- relentless seizures may ensue.
  • The drug withdrawal category also includes the abrupt cessation of (or noncompliance with) regular antiepileptic therapy in a known epileptic.

Idiopathic neurological causes:

  • By this, I mean poorly controlled epilepsy. It is possible to be fully compliant with your medications and still find them totally ineffective.

 

Congenital causes:

  • Some people are  extremely unlucky, and suffer from some sort of rare congenital disorder of metabolism which will occasionally surmount their carefully coordinated diet, and flood their brain with toxic metabolic byproducts.
  • Alternatively, one can have a structural; congenital abnormality, such as cerebral palsy.

Autoimmune causes:

 

Traumatic causes

  • Typically, one does not have relentless seizures with trauma. However, seizure disorders in general can develop follwoign head injury, particularly severe ehad injury and situations when something sharp actually penetrates the brain tissue.
  • In that sense, neurosurgical procedures could also be viewed as a risk factor.

Endocrine and metabolic causes

  • Apart from the abovementioned rare disorders of metabolism, common metabolic disturbances could result in status epilepticus.
  • Specifically, Oh’s Manual lists a series of electrolyte distrubances – which are all hypo-something. Hyponatremia, hypokalemia, hypomagnesemia, hypocalcemis – all seem to cause status epilepticus. Why do disorders of electrolyte excess not cause it? No answer is available from the Manual.
  • An extremely low or extremely high BSL are equally likely to cause seizures.
  • Uremic encephalopathy and hepatic encephalopathy complete the list of metabolic causes.

 

References

Oh's Intensive Care manual:

Chapter 49   (pp. 549) Disorders  of  consciousness  by Balasubramanian  Venkatesh

Chapter   50   (pp. 560) Status  epilepticus  by Helen  I  Opdam

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