DISORDERS OF HYPOTHALAMUS

DISORDERS OF HYPOTHALAMUS

The lesion of hypothalamus occurs due to tumors, encephalitis and ischemia. Following features develop

in hypothalamic lesion:

1. Disturbances in carbohydrate and fat metabolisms, when lateral, arcuate and ventromedial nuclei are involved in lesion

2. Disturbance in sleep due to lesion in mamillary body and anterior hypothalamus

3. Disturbance in sympathetic or parasympathetic function occurs due to lesion in posterior, lateral and anterior nuclei

4. Emotional manifestations, leading to sham rage due to lesion in ventromedial and posterolateral parts

5. Disturbance in sexual functions due to the lesion in midhypothalamus.

One or more of the above features can become prominent, resulting in some clinical manifestations

such as:

1. Diabetes insipidus

2. Dystrophia adiposogenitalis

3. Kallmann syndrome

4. Laurence-Moon-Biedl syndrome

5. Narcolepsy

6. Cataplexy.

DIABETES INSIPIDUS

Diabetes insipidus is the condition characterized by excretion of large quantity of water through urine.

DYSTROPHIA ADIPOSOGENITALIS

This condition is characterized by obesity and sexual infantilism, associated with dwarfism (if the condition

occurs during growing period). It is also called Fröhlich syndrome.

KALLMANN SYNDROME

Kallmann syndrome is a genetic disorder characterized by hypogonadism, associated with anosmia (loss of olfactory sensation) or hyposmia (decreased olfactory sensation). It is also called hypogonadotropic

hypo gonadism, since it occurs due to deficiency of gonadotropin-releasing hormones, secreted by hypothalamus.

LAURENCE-MOON-BIEDL SYNDROME

This disorder of hypothalamus is characterized by moon face (facial contours become round by hiding the

bony structures), obesity, polydactylism (having one or more extra fingers or toes), mental retardation and hypogenitalism.

NARCOLEPSY

Narcolepsy is a hypothalamic disorder with abnormal sleep pattern. There is a sudden attack of uncontrollable desire for sleep and the person suddenly falls asleep. It occurs in the daytime.

The sleep may resemble the normal sleep. The duration of sleep is very short. It may be from few

seconds to 20 minutes. In night, sleep may be normal but is often disturbed or there may be insomnia (loss of sleep).

CATAPLEXY

Cataplexy is the sudden uncontrolled outbursts of emotion associated with narcolepsy. Due to emotional

outburst like anger, fear or excitement, the person becomes completely exhausted with muscular weakness. The attack is brief and last for few seconds to a few minutes. Consciousness is not lost.

Role of Reward and Punishment Centers

The importance of the reward and punishment centers lies in the behavioral pattern of the individuals. Almost all the activities of day-to-day life depend upon reward and punishment. While doing something, if the person is rewarded or feels satisfied, he or she continues to do so. If the person feels punished or unpleasant, he or she stops doing so. Thus, these two centers play an important role in the development of the behavioral pattern of a person.

Rage

Rage refers to violent and aggressive emotional expression with extreme anger. It can be developed

in animals by stimulating the punishment centers in posterior and lateral hypothalamus. The reactions of

rage are expressed by developing a defense posture, which includes:

i. Extension of limbs

ii. Lifting of tail

iii. Hissing and spitting

iv. Piloerection

v. Wide opening of eyeballs

vi. Dilatation of pupil

vii. Severe savage attack even by mild provocation.

Sham Rage

Sham rage means false rage. It is an extreme emotional condition that resembles rage and occurs in some pathological conditions in humans. In physiological conditions, the animals and human

beings maintain a balance between the rage and its opposite state. This balanced condition is called the calm emotional state. A major irritation may make a person to loose the temper. However, the minor irritations are usually ignored or overcome. It is because of inhibitory influence of cerebral cortex on hypothalamus. But the calm emotional state is altered during brain lesions. In some cases, even a mild stimulus evokes sham rage. It can occur in decorticated animal also. Sham rage is due to release of hypothalamus from the inhibitory influence of cortical control.

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