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Hypothalamic Lesion

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Hypothalamic Lesion from the Perspective of Neurologist and Neurosurgeon


The hypothalamus is a substructure of the diencephalon and acts
as one of the most significant control centers of the brain. It
is located inferior to the thalamus, encapsulates the ventral
portion of the third ventricle, and lies just superior to the
pituitary gland, which it has direct regulatory control over
(Gunderson, 1996). Neurosecretory neurons in the hypothalamus
secrete releasing and inhibiting hormones which are carried to
the anterior pituitary where they exert their effects via
hypothalamic-hypophyseal portal veins. Included in the many
functions of the hypothalamus are regulation of food and water
intake, autonomic function, emotions, body temperature, motor
functions, and circadian sleep-wake cycles (Kalat, 2004).
Hormones secreted by the hypothalamus include Thyrotropin-
releasing hormone, Gonadotropin-releasing hormone, Growth-
releasing hormone, Corticotropin-releasing hormone,
Somatostatin, and Dopamine (Klaus,n.d.).

Medically, a lesion is a term referring to abnormal tissue
in the body that can be caused by many factors including
disease, trauma, infection, or neoplasm which is an abnormal
growth of tissue, such as a tumor (Healthopedia.com, n.d.). For
the purpose of this paper tumor and lesion will be used
interchangeably.

As a neurologist I am a medical doctor with specialized
training in diagnosing, treating, and managing disorders of the
brain and nervous system, including diagnosis of brain tumors.
As a professional I act as the primary care provider for
patients with chronic neurological problems and as a consultant
to other physicians who have clients suspected of having a
condition involving the nervous system (Life NPH, n.d.). A
neurological examination allows me to effectively diagnose the
condition of the patient and suggest appropriate treatment
options. I first review the patient's health history with
special attention to the current condition. A patient suspected
of having a disorder of the nervous system will be subjected to
a general neurological examination which includes testing of eye
movement and pupil reaction, hearing, reflexes, balance and
coordination, sense of touch, sense of smell, facial muscle
functioning, gag reflex, head movement, mental status, abstract
thinking, and memory (Malhi, 2000).

A full neurological examination is generally administered,
despite any preconceived opinions of a patient’s potential
ailment, in order to illustrate the condition as clearly as
possible and rule out any alternative diagnosis. An examination
takes 90 minutes or more in most cases and consists of a battery
of tests. A neurological exam tests for a client’s level of
function of the area of the nervous system involved in a given
task, thus each segment of the exam must cover a scope from easy
to difficult to accommodate for naturally occurring differences
between individuals (Neuroexam.com, n.d.). For the purpose of
this paper it is not realistic or necessary to describe each
step of the exam but I will give a few examples to demonstrate
the types of tests involved.

The optic nerve (cranial nerve II) should be tested for
function of visual fields, visual acuity, and fundoscopy. To
test visual fields I ask the patient to shut their left eye and
look straight into my right eye. I introduce a pinhead (white
for peripheral field testing and red for central field) into the
patient’s field of vision midway between us and from several
different directions. Each time, the patient reports its
appearance as soon as it is detected. Visual acuity is tested by
having the patient read from eye charts from varying distances
for near and far vision. Fundoscopy is the examination of the
retina which is best done in a dark room so that the pupils are
better able to dilate. The patient stares at a fixed point in
the distance and I approach each eye in turn with an
opthalmoscope from an angle of approximately 15 degrees
(Malhi,2000).

Testing of the noncortical sensory system involves testing
for responses to tactile stimulation, temperature, and
vibration. To test light touch I have the patient close their
eyes and gently touch their skin in various areas with a piece
of cotton and have them report whether they feel the touch or
not (Neuroexam.com, n.d.). To test pain I once again have the
patient close their eyes and randomly apply a blunt or sharp
stimulus in random patterns, then have the patient report the
nature of the stimulus. To test temperature I apply a hot or
cold tube of water to the patient’s skin. Vibration is tested by
pressing a quivering tuning fork against a bony prominence, such
as the patella, and having the client report to what extent they
feel a vibration (Malhi, 2000).

In some cases, lesions of the hypothalamus may present no
overt symptoms but generally, a variety of neurological,
hormonal, and ophthalmologic symptoms cause a person to seek
help and lead the clinician to an accurate diagnosis.
Hypothalamic tumors that extend into the area of the pituitary
may lead to endocrine, visual, and neurological symptoms
comparable to those observed in patients with pituitary tumors.
The triad of symptoms that present the clearest indication of a
hypothalamic tumor are hypogonadism, central diabetes insipidus,
and visual disturbances. Hypogonadism is a deficiency of sex
hormone secretions from the gonads. Central diabetes insipidus
is a condition where the kidneys are unable to conserve water
during their filtering process due to abnormal secretion and
storage of ADH (Antidiuretic hormone or vasopressin) by the
hypothalamus and pituitary gland. Visual disturbances occur as a
result of the tumor compressing an area of the optic tract or
chiasma (Klaus,n.d.).

Other symptoms of a hypothalamic lesion include weight
loss or gain, paleness, excessive sweating, tremor or shakiness,
irritability, involuntary eye movements, euphoria, headaches
that tend to be worse during the morning, and, in children,
failure to thrive, which is a lack of normal growth (Cook,
1996).

The ventromedial region of the hypothalamus is responsible
for triggering satiety, and thus cessation of eating and
drinking behavior, and the lateral region of the hypothalamus is
involved with the initiation of eating and drinking.
Hypothalamic lesions, depending on their exact location, can
cause abnormal control of satiety which may lead to hyperphagia
(gross overeating) and eventual obesity or, in the opposite
direction, to cachexia (loss of body fat and appetite) (Klaus,
n.d.).

If the physical portion of the neurological examination
indicates the likelihood of a brain tumor I will then recommend
that the patient undergo further diagnostic testing involving
brain scans and/or a lumbar puncture. Brain scans are able to
provide an image of the brain that includes regions behind bone.
Common diagnostic scans for brain lesions include CAT and MRI
scans.

Before a CAT scan the patient is injected with a dye-like
solution that provides the x-ray device and computer a clearer
contrast between healthy and abnormal tissue. The patient is
placed on a flat surface that slides into a doughnut-shaped
opening (American Brain Tumor Association, n.d.). The scanner
circles the patient’s head, creating images of the brain based
on penetrating x-rays. The imaging portion of the procedure
should only take 10-15 minutes (Malhi, 2000).

The MRI is more sensitive than a CAT scan in detecting
brain lesions as it provides a higher resolution but it also
tends to be more expensive and is contraindicated for people
with any type of metal implant in their body (Malhi, 2000). The
patient lies on a table that slides inside of the tunnel-shaped
MRI. No x-rays are used in this procedure but instead a magnetic
field affects the movement of the atoms in the brain. Antennas
detect signals from the atoms and relay information to a
computer which pieces together an image of the brain (American
Brain Tumor Association, n.d.)

Brain scans can give important information about the
nature, location, and stage of a person’s lesion. They play a
vital role in planning and implementing treatment.

As a neurosurgeon I am trained in the operative and non-
operative diagnosis, management, prevention, and treatment of
neurological disorders. Incorporating diagnostic information and
opinions from other physicians and neurological specialists,
such as primary physicians, neurologists, and
nueropsychologists, I determine the most effective plan of
treatment for the given patient (Life NPH, n.d.).

Surgery is the preferred treatment for tumors and lesions
located within the brain but some areas of the brain may be
inoperable due to location or quality of the lesion. Among the
brain areas that are often deemed inoperable are the brain stem,
motor area, thalamus, and some areas of gray matter (University
of Chicago Department of Surgery, n.d.).

If a lesion is deemed surgically accessible and further
diagnostic information would be helpful in planning treatment,
then I will generally perform a biopsy A biopsy is a surgical
procedure in which a small quantity of the tumor is removed for
examination by a neuropathologist. For those areas of the brain
not easily accessible via an open biopsy, stereotaxic biopsy is
often employed. This process entails drilling a small hole in
the skull and inserting a narrow, hollow needle which is guided
via sterotaxic instrumentation to the location of the tumor.
Tumor tissue is then removed from the center of the needle and
examined by a neuropathologist to arrive at an accurate
diagnosis and classification of the lesion (American Brain Tumor
Association, n.d.).

There are many different types of lesions that may occur
at the site of the hypothalamus or that may affect it
indirectly. Hypothalamic lesions can occur at any age but many
are developmental and present themselves during childhood. Some
classifications of hypothalamic lesions include
craniopharyngioma, glioma, germinoma, chordoma, and hamartoma.
Craniopharyngiomas are benign but their growth often infiltrates
and causes adverse effects upon other brain structures
(Klaus,n.d.). Most hypothalamic tumors in children are gliomas
which originate from the supportive glial cells of the brain.
The presence of certain genetic syndromes, such as
neurofibramotosis, increases the risk of developing gliomas
(Gunderson, 1982). Germinomas develop from germ cells and are
most frequently observed in adult males. In younger patients
germinomas often present themselves through precocious puberty,
a condition in which the onset of puberty is significantly
premature, often before the age of eight (Klaus,n.d).

Some types of hypothalamic lesions are inoperable due to
the nature, specific location, and grade of the tumor.
Fortuantely there are some, most craniopharyngiomas for example,
that are surgically accessible. When determining whether surgery
is a viable option for a given patient I have to take into
consideration the exact location of the offending lesion, the
surrounding structures that may be affected by surgery, the age
and health of the patient, and whether alternative therapies may
provide a more effective or safer treatment option (American
Brain Tumor Association, n.d.).

As mentioned previously, surgery is the preferred option
for the most effectual treatment of brain tumors. The goal of
tumor resectioning is to remove as much of the tumor as
possible. A patient who will be undergoing brain surgery is
generally admitted to the hospital the day before surgery.
Before the day of surgery I will meet with a patient to answer
questions and discuss the surgical procedure, possible risks and
benefits, and alternative treatments. Generally surgical
resection of a tumor is executed by means of a craniotomy. A
craniotomy entails the removal of a piece of skull bone which is
replaced and secured back into place after surgery (American
Brain Tumor Association, n.d.).The patient usually lies on their
back and a general anesthesia, which causes the patient to
remain unconscious during the operation, is administered prior
to the beginning of the procedure. The area where I will be
making the incision is shaved and cleaned. I then make an
incision in the scalp and use a surgical saw to remove a portion
of bone over the brain area containing the tumor. Carefully, I
slice through the membranes surrounding the brain and use an
assortment of specialized tools to remove the abnormal growth
from the brain (The University of Chicago Department of Surgery,
n.d.). Some of the tools I might employ include a surgical
laser, an operating microscope, ultrasonic aspirator, and
stereotactic instrumentation (American Brain Tumor Association,
n.d.). When I feel that sufficient removal has been completed, I
will replace the membranes and skull bone and stitch the skin
back together.

Brain surgery can be a highly effective treatment but it
also poses the threat of serious complications such internal
bleeding, infection, brain damage, and death (The University of
Chicago Department of Surgery, n.d.). If removal of the tumor
was successful then the patient can expect a positive prognosis
regarding recovery rate and expected mortality.

Radiation and chemotherapy may be used as secondary
therapies if there is a question to the success of the surgery.
They may also be used as primary therapies if brain surgery is
too risky or not considered necessary. Radiation is the use of
high energy x-rays to destroy abnormal cells or to alter their
metabolism and thus alter their ability to function.

Chemotherapy involves the use of cytotoxic drugs to destroy
cancerous cells by interfering with their ability to reproduce
themselves (National cancer Institute, n.d.).

Sources Cited

American Brain Tumor Association.(n.d.). Fifth Edition A Primer
of Brain Tumors: A Patient’s Reference Manual.
http://neurosurgery.mgh.harvard.edu/abta/primer.htm . (Retrieved
April 19, 2005).

Bast, R.C. (Ed), Kufe, D.W. (Ed), Holland J.F. (Ed), & Frei,E.
(Ed).(2003). Cancer Medicine, 6th edition. Ontario: B.C. Decker

Cook, A.R. (Ed). (1996). The New Cancer Sourcebook. Detroit:
Omniographics.

Gunderson, C. H.( 1982). Quick Reference to Clinical Neurology.
Philadelphia: J.B. Lippincott

Healthopedia.com. www.healthopedia.com (Retrieved April 19,
2005).

Klaus.W. (n.d.) Endotext.com. Pituitary-Hypothalamic Tumor
Syndromes: Adults www.endotext.org (Retrieved April 22, 2005).

Life NPH.(n.d.). http://www.allaboutnph.com (Retrieved April
21,2005)

Malhi, G.S. (2000). Neurology for Psychiatrists. London: Martin
Dunitz Ltd.

National Cancer Institute. www.nci.nih.gov (Retrieved May
2,2005)

Neuroexam.com. (n.d.). www.neuroexam.com (Retrieved May 1,
2005).

The University of Chicago Department of Surgery. (n.d.)
http://surgery.uchicago.edu/neurosurgery/brainsurgery.cfm
(Retrieved May 2, 2005)

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