Category: Neurology

SAH – NICE 2022

Headache is a common presentation to ED and Subarachnoid Haemorrhage (SAH) is the diagnosis we never want to miss. However, working out who needs a scan can be difficult as 50% of patients presenting with a subarachnoid have no neurological deficit.

  • ‘Thunder Clap’ headache peak of pain within 5min is a RED-FLAG
    • Although, most patients with ‘Thunder Clap’ don’t have SAH, this should not deter emergent investigation
  • Patients may present more subtlety the following should make you consider the diagnosis:
    • neck pain or stiffness (limited or painful neck flexion on examination)
    • photophobia
    • nausea and vomiting
    • new symptoms or signs of altered brain function (such as reduced consciousness, seizure or focal neurological deficit)
  • Always be suspicious if the patient has communication difficulties.

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Nitrous Oxide Induced Neurotoxicity

Nitrous Oxide  has been used clinically and recreationally since its discovery in 1772. Since then Nitrous Oxide induced neurotoxicity have been reported, and has been shown to be dose depaendant. With infrequent users unlikely to be at risk of neurotoxicity, while heavier and habitual used at risk of serious neurological conserquences.

With the increase in recreation use of “Whippits” we need to remember to take a detailed recreation drug history when seeing patients presenting to ED with neurological symptoms. As Nitrous Oxide induced neurotoxicity is treatable.


Nitrous Oxide induced neurotoxicity can present as either spinal cord demyelination , peripheral neuropathy or a a combination of the two.

  • Demyelination of the dorsal columns of spinal cord 
    • Typically onset is subacute  (i.e. weeks), but acute onset has been reported in the literature
    • Typically symmetrical but can be unilateral
    • Signs
      • Pyramidal weakness – weak upper limb extensors, and lower limb flexors
      • Dorsal Column Sensory loss – Vibration, Proprioception, Fine touch
      • Sensory Ataxia – Incoordination due to loss of proprioception and weakness
    • Level – Most frequently cervical 4-6 levels, but can affect any.
  • Peripheral Neuropathy
    • Typically Symmetrical (but not always)
    • Sensory loss (often painful)
    • Distal Weakness
  • Optic Neuropathy  – has been reported and may present with visual disturbance.


Nitrous Oxide usage can render vitamin B12 inactive, which in-turn disrupts myelination, causing the demyelination of nerves.


  • Deficiencies: B12, Folate, copper, zinc
  • Inflammatory: Guillian-Barre syndrome, MS, Neurosarcoidosis
  • Infection: HIV, Syphilis
  • Cancer
  • Vascular: Spinal cord ischaemia, vasculitis


  • Vitamin B12 level (often in normal range)
  • Homocysteine and Methylmalonic Acid Level (not available in ED)
  • MRI – contrast enhanced


Start before Tests are back (i.e. on clinical suspicion)

  • IM Vitamine B12 1mg OD
  • PO Folic Acid 5mg OD


  • Discuss admission with Medical team as potential for SDEC management
  • Treat until clinical improvement(King’s Team noted the following)
    • Sometimes treat for 5-7days only
    • Often switch to alternate days IM Bit B12
    • Can teach to self administer
  • Further Testing
    • Homocysteine and Methylmalonic Acid levels – often improve quickly
    • MRI often lags clinical improvement endnote necessary to repeat
  • Majority Improve clinically – but futureabstinence is often challenging



Cervical (Carotid OR Vertebral) Artery Dissection

Cervical artery dissection is a rare but significant cause of stroke and headache/neckache, which is easy to overlook. Leading to a typically delay in diagnosis of 7 days. Unfortunately imaging the cervical arteries is not simple, with MRA being the method of choice. Hence these patients must be referred to the “Stroke Consultant”.

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COVID-19 Vaccine Induced Thrombosis/Thrombocytopenia (VITT)

Inclusion Criteria [Both of]:

  1. Received AstraZeneca (AZ) COVID 19 vaccination within 42 days (typically 5-42 days from immunisation)
  2. New Onset thrombocytopenia (PLTs <150×109/L) – with or without Thrombosis
    • 5% of cases have had a “Normal” Platelet count at presentation
      • High index of suspicion repeat bloods next day
      • ‘High index of suspicion’ in this context is day 5- 28 post AZ vaccine with new onset headache or abdominal pain which is atypical and severe in nature.

Initial Investigations:

  • FBC– specifically to confirm thrombocytopenia <150x 109/L
  • Coagulation screen and D Dimers
  • Blood film to confirm true thrombocytopenia and identify alternative causes

PROBABLE CASE: (ALL 3 criteria)

  1. Received AZ COVID 19 vaccination within 42 days
  2. New Onset thrombocytopenia (PLTs <150×109/L)
  3. D Dimers > 2000 mcg/L

URGENT Scan to confirm the suspected clot.

[If patient doesn’t fit “PROBABLE CASE” proceed to usual treatment]

Condition specific advice:

Central clot:

  • inc. Cerebral Venous Sinus Thrombosis (CVST), Pulmonary Embolis (PE), Splenic, Proximal DVT
  • Discuss with Haematologist
  • Admit Medicine

Suspected DVT (scan unavailable):

  • Treat with Rivaroxaban (Do Not use Tinzaparin/LMWH)
  • Request Ultrasound
  • Return AAU Next Day
  • Safety-net Advice

Confirmed Distal DVT (Not above inguinal ligament)

  • Platelets  <100×109/L – Discus with Haematology
  • Platelets ≥100×109/L – Treat as normal

Thrombocytopenia only

  • Platelets  <100×109/L – Discus with Haematology
  • Platelets ≥100×109/L – Treat as normal

Treatment (will be directed by Haematology & Specialist teams):


  • Heparin Based anticoagulants
  • Antiplatelets
  • Platelet Transfusion

May Require:

  • IV immunoglobulin
  • Steroid
  • Anticoagulation with: DOAC, Fondaparinux, Argatroban

Further reading