Showing posts with label its. Show all posts
Showing posts with label its. Show all posts
Monday, March 16, 2015
Migraine and its types
it has been estimated that 18 million women and 6 million men in the United states suffer from sever Migraine headaches.
Migraine can usually be distinguished clinically from the two other common types of headaches :
Migraine: present as a pulsatile,throbbing pain
a. Cluster headaches : as excruciating,sharp and steady pain.
b. Tension-type headaches: as dull pain,with a persistent,tightening feeling in the head.
Patients with severe migraine headaches report one to five attacks per month of moderate to severe pain, usually unilateral. The headaches affect patient for a major part of their lives and result in considerable health losts.
Types of Migraine
There are two main types of migraine headaches.
The first, migraine without aura(previously called common migraine), is a severe,unilateral,pulsating headaches that typically lasts from 2 to 72 hours. These headaches are often aggravated by physical activity and are accompained by nausea, Vomiting , Photophobia (hypersensitivity to light), and Phonophobia (hypersensitivity to sound).
Approximately 85 percent of patients with migraine do not have aura.
In the Second type, Migraine with aura (previously called classic migraine),
the headache is preceded by neurologic symptoms called auras,which can be visual,sensory,and/or cause speech or motor disturbances.Most commonly,these prodromal symptoms are visual, occuring approximately 20 to 40 minutes before headache pain begins. In the 15 percent of Migraine patients whose headaches is preceded by an aura, the aura itself allows similar.
For both types of Migraine, women are three-fold more likely than men to experience either type of Migraine.
BIOLOGIC BASIS OF MIGRAINE HEADACHES:
The first manifestation of migraine with aura is a spreading depression of neuronal activity accompanied by reduced blood flow in the most posterior part of the cerebral hemisphere. This hypoperfusion gradually spreads forward over the surface of the cortex to other contiguous areas of the brain. The vascular alteration is accompanied by functional changes; for example, the hypoperfused regions show an abnormal response to changes in arterial partial pressure of CO2. The hypoperfusion persists throughout the aura and well into the headache phase, after which hyperperfusion occurs. Patients who have Migraine without aura do not show hypoperfusion. However the pain of both types of Migraine may be due to Extracranial and Intracranial arterial dilation. This stretching leads to release of neuroactive molecules, such as Substance P.
Sunday, March 15, 2015
The Thalamus as its Relay function
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the thalamus is a part of diencephalon and has multiple functions. It translates information from all sensory pathways other than Olfaction and selectively distributes those impulses to appropriate parts of the cortex (relay function). The following thalamic nuclei receive input from sensory pathways:
1.Ventral posterolateral (VPL) receives input from the spinothalamic tract (pain and temperature sensation) and medial lemniscus(position and proprioception). It transmits impulses to primary somatosensory cortex (Brodmann areas 3,1 & 2).
2.Ventral posteromedial nucleus (VPM) receives inputs from the trigeminal and gustatory pathways and transmits them to the primary sensory cortex (Brodmanns areas 3, 1 & 2).
3.Lateral geniculate body is a relay nucleus for the vision pathway. It receives impulses from the optic nerve and transmits them via the optic radiations to the visual cortex (calcarine sulcus)
4.Medial geniculate body is a part of the auditory pathway. It receives impulses from the superior olivary nucleus and the inferior colliculus of the pons, and projects them to the auditory cortex of the temporal lobe (Brodmann areas 41 & 42)
The olfactory tract is the only sensory pathway where input is not processed through thalamus.
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