Colobomas

A coloboma is a congenital malformation in which part of the eye does not form due to failure of fusion of embryonic structure called the intraocular fissure.  This malformation can occur unilaterally or bilaterally and causes the eye to protrude anteriorly or posteriorly.  There are many places a coloboma can occur; the iris, the lens, the choroid, the eyelid, the optic disc, or the retina.  Colobomas are present at birth and usually affect 1 out of every 10,000 births.  A coloboma can occur due to surgery, trauma or may be hereditary.   If a child is diagnosed with a coloboma it is suggested that the parent have an eye exam because this condition can be present without any vision problems. The effect this condition has on vision depends on where in the eye the coloboma is located and how big the gap is. One example of a vision defect is a dislike to bright lights, which usually occurs in those with a coloboma in the iris.   The key finding in children with this condition is a key-hole shaped pupil and may be diagnosed with the help of an ophthalmologist and MRI exam.  A coloboma is typically identified on an MRI T2 weighted image as a hypodense protrusion of the orbital globe. Children affected by colobomas sometimes have an accompanying rare condition called CHARGE syndrome, which stand for; coloboma, heart defects, atresia of the choanae (problems with the nose passage), retarded growth and development, genital hypoplasia (undescended testicles), ear abnormalities.   Currently there is no treatment for colobomas, except that the child will have help from a specialist to determine the effects and problems of the coloboma.  Most children will be required to have eye exams every six months until the age of seven and then yearly after the age of seven, and will be prescribed sunglasses to help with light sensitivity.

                              Pediatric MRI T2 weighted image of a coloboma on the right side.

                                           Key-hole shaped pupil in a child with a coloboma.

Acromegaly

Acromegaly is a tumor of the pituitary gland that causes increased thickening of the bones in the hands, feet, cheeks and jaw.  Acromegaly occurs in about 6 of every 100,000 adults and is usually caused by the production of excessive growth hormone after the skeleton is finished growing.  This overproduction of growth hormone is a result of a benign tumor of the pituitary gland.  Some common symptoms include but are not limited to; impaired vision, body odor, carpal tunnel syndrome, decreased muscle strength, easy fatigue, headache, excessive height, enlarged hands, feet, jaw and tongue, limited joint movement, thickening of the skin, and excessive hair growth in females.  This disease is most often diagnosed in middle-aged adults, but can appear at any age.  Patients with acromegaly are at high risk for developing type II diabetes, hypertension, sleep apnea syndrome, cardiovascular disease, arthritis, and colon polyps which could develop into cancer if left untreated.

Acromegaly is usually diagnosed utilizing several different tests.  Two of the usual tests are the growth hormone blood test and oral glucose tolerance test to determine if the patient has excessive growth hormone in the body.  Likewise the physician also uses imaging modalities after growth hormone tests to determine location and size of the tumor.  The physician will most likely order an MRI of the pituitary gland.  The MRI technologist will utilize sagittal and coronal T1 weighted spin echo images before and after the use of gadolinium.   In most cases a macroadenoma (tumor bigger than 10mm) will be found.  In a gadolinium enhanced MRI acromegaly is usually seen as a hypodense area where the pituitary gland is located.

There are usually three approaches to treatment for acromegaly; surgery, medical therapy, and radiation therapy.  Surgery is usually the first option and usually has the best outcomes.  During surgery the surgeon simply removes the tumor, which relieves the pressure and allows the hormone levels to lower.  It is important to note that even after surgery there is a chance of reoccurrence so patients may need medications and may need to continue to be monitored.  Medical therapy uses three classes of drugs (SSAs, GHRAs, Dopamine antagonists) for treatment in patients who are unable to have surgery or to shrink a tumor prior to surgery.  Radiation therapy is used for patients who still have some tumor left after surgery or whose bodies are unresponsive to medications, although it is important to note the effects of radiation therapy may not be seen for years.

                     The picture above shows a common symptom, enlargement of the hands.

       MRI image of a macroadenoma in acromegaly.  The image on the right shows the tumor

is only about 9mm in size. The tumor is far enough away that there is no impairment of vision.

MRI image of pituitary macroadenoma in an acromegalic patient.  The picture on the right shows the tumor with a diameter of 30mm.  The optic chiasm is elevated and compressed causing the patient loss of peripheral vision.

Mesial Temporal Sclerosis

Mesial temporal sclerosis (MTS) is also known as hippocampal sclerosis.  This condition is closely related to temporal lobe epilepsy, which simply means that the start of the seizure can be identified within the temporal lobe of the brain.  Mesial temporal sclerosis is due to the loss of neurons and results in the scarring of the hippocampus due to certain brain injuries.  These brain injuries include but are not limited to infection, traumatic injury, tumors, and lack of oxygen to the brain.  Common symptoms include strange sensations, changes in behavior or emotions, muscle spasms, and convulsions.  MTS occurs in 65% of epilepsy patients in autopsy studies. MTS treatment usually includes anti-epileptic medications or temporal lobectomy.

Mesial temporal sclerosis is best viewed using MRI.  The best imaging planes to detect MTS are the coronal plane and the axial plane.  The coronal plane is able to detect volume reduction and T2 signal change while the axial plane is able to detect the posterior extent of hippocampal abnormalities.  Likewise gradient echo techniques are used rather than spin echo due to the smaller slice thickness.  Because gradient echo allows for smaller slice thickness it allows for better imaging of gray and white matter.  On a typical MRI study showing MTS you may find the following abnormalities; reduced hippocampal volume, increased T2 signal, loss of gray and white matter interface in the anterior temporal lobe, atrophy of the ipsilateral fornix and mammillary body.

Above is a video showing MRI images of MTS along with a short clip of a left mesial temporal sclerosis with calcified lesion removal.