Headache

Classification:

• The Primary Headache.
• The Secondary Headache.
• Cranial Neuralgia, Central and primary facial pain and other headaches.

Primary headaches include migraine, cluster headache and tension headache.

Secondary headaches can be divided into intracranial and extracranial causes.
Intracranial:
Raised intracranial pressure
Vascular - Cerebral infarct, intracerebral haemorrhage, subarrhanoid haemorrhage, subdural haemorrhage and extradural haemorrhage.
Non-vascular - Abscess, Meningitis, Encephalitis, Tumor, benign intracranial hypertension and congenital lesion.
Reduced intracranial pressure - lumbar puncture, CSF leakage following head injury.

Extracranial: can be subdivided into local and systemic causes.
Local - examples includes refractive errors of eyes, glaucoma, sinusitis, dental disorder and cervical spondylosis, etc.,.
Systemic - carbon dioxide retention, hypoglycemia, Depression, Fever.

The aim of this blog is about medically important headaches which must not be missed.
1) Thunderclap headache
2) Intracranial infection especially encephalitis

Thunderclap headache
Thunderclap headache refers to a severe and explosive headache with peak intensity at onset. Diagnostic criteria includes:
1) very severe pain intensity
2) Instantaneous or hyperacute onset of pain ( less than 30 seconds )

Thunderclap headache is a clinical emergency which mandates a swift evaluation with investigations aimed at excluding a subarachnoid haemorrhage.

The differentials diagnosis for thunderclap headache include:

• Subarachnoid haemorrhage
• Cerebral Venous Sinus Thrombosis
• Cervicocephalic arterial dissection
• Acute hypertensive crisis
• Spontaneous intracranial hypotension
• Pituitary apoplexy
• Benign thunderclap headache
  

These disorders with the exception of subarachnoid haemorrhage may often evade detection by CT and lumbar puncture.

Cerebral Venous Sinus Thrombosis

75% of CVST present with headache which is often persistent, worse upon recumbancy and aggravated by the valsalva manoeuvre. 40 % of CVST patients may have raised intracranial pressure without alteration of CSF cytochemistry studies.

When there is clinical suspicion of CVST, CT has now been supplanted by MRI, which should now be initial investigation.

Cervicocephalic arterial dissection
Unilateral headache, especially in the anterior head region is strongly suggestive of internal carotid artery dissection. There can be delayed focal cerebral ischaemic events.
MR angiography is fast becoming the imagin modlity of choice in demonstrating the arterial dissection.

Pituitary Apoplexy
It is characterised by acute headache, ophthalmoplegia, diminished visual acuity and altered mental status caused by the sudden infarctionor haemorrhage of a pituitary gland.

Benign ( idiopathic ) thunderclap headache
It is a diagnosis of exclusion and so, in the absence of organic intranial pathology, thunderclap headache may occur as a benign and potentially recurrent idiopathic headache disorder.

Diagnostic Evaluation of thunderclap headache:

Brain CT is a must in all patients. The sensitivity of subarachnoid haemorrhage is 98 % within the first 12 hr of onset of headache and 93 % within the first 24 hours. However, sensitivity decreases to 86% after day 1 and 76 % after day 2.

Lumbar puncture is therefore required in all patients whose initial CT is negative, equivocal or technically inadequate.

In cases where the CSF or clinical findings are difficult to interpret or the index of suspicion is unusually high ( family or personal history of subarachnoid haemorrhage ) MRA is an appropriate procedure.

Viral Encephalitis:

Acute encephalitis constitutes a neurological emergency and it is imperative that appropriate treatment is started as soon as possible.

1. Establishing the diagnosis of encephalitis
Three differentials for acute or subacute causes of confusion includes

1. Infective encephalitis
2. Acute disseminated encephalomyelitis
3. Encephalopathy/delerium

Acute disseminated encephalomyelitis may be distinguished from infective encephalitis by the younger age of the patient, prodromal history of vaccination or infection, absence of fever at the onset of symptoms and the presence of multiple neurological signs affecting optic nerves, brain, spinal cord and peripheral nerve roots.

Infective encephalitis is suspected in a febrile patients who presents with altered consciousness and the presence of focal neurological signs and focal seizures. However, cerebral malaria is considered to an example of infective encephalopathy rather than encephalitis since the neurological symptoms of cerebral malaria result from brain hypoxemia and metabolic complications ( hypoglycemia and acidosis ) due to heavy parasitaemia leading to capillary occlusion.

2. Establishing the cause of infective encephaltitis