3-year-old (Male) with Deviation of His Left Eye

00:01 Okay, guys. We have an absolutely important question here.

00:05 Very high yield and classic for USMLE. Let's jump right in.

00:10 A 3-year-old old boy presents to his pediatrician for a regular checkup.

00:15 The patient's mother is concerned about a slight deviation of his left eye.

00:21 She started to note it a year ago.

00:23 She also notes that her child's left eye looks strange on photos, especially if there is a flash.

00:30 The patient is the first child in the family born to a 31-year-old woman from an uncomplicated pregnancy.

00:38 He has been developing normally and did not suffer any major diseases.

00:44 His family history is unremarkable.

00:47 The eye examination shows left eye convergent strabismus.

00:51 The pupillary reflect cannot be elicited from an illumination of the left eye.

00:57 A fundal examination is shown in the picture.

01:07 On testing, visual evoked potentials cannot be elicited from the left retina but is normal from the right retina.

01:16 MRI of the orbit shows a retina-derived tumor in the left eye with an initial spread along the intrabulbar part of the optic nerve and vitreous seeding.

01:28 The other eye is completely intact.

01:31 Which of the following methods of treatment is indicated for this patient? Answer choice A: Brachytherapy; Answer choice B: Chemotherapy; Answer choice C: Eye enucleation; Answer choice D: Cryotherapy; or Answer choice E: Laser coagulation Now take a moment to come to the answer by yourself before we go through it together.

02:02 Like we were saying, this is an important question, very high yield.

02:06 The USMLE loves this diagnosis.

02:09 So, let's discuss the question characteristics.

02:12 Now, this is actually a surgery question.

02:14 Surgical ophthalmology involving the eye, but definitely surgery.

02:19 It's a 2-step question.

02:21 The first thing we have to do is determine the diagnosis and then the second stage is to figure out the best plan and of course, a stem is required because not only do we need to go to the details of the question to know what's going on to reach the diagnosis, we also need the image which helps us a lot.

02:37 So, let's walk through this question.

02:40 Now we have a 3-year-old male patient coming in with a chief complaint related to his left eye.

02:45 He has eye symptoms of the left eye only, including deviation, a strange look on his eye in the photos and what they're trying to get out there is a white reflex.

02:55 No pain, no secretions and gradual onset in which the symptoms were first noticed one year ago.

03:02 Now the patient history is unremarkable -- his pregnancy and he hasn't had any problems himself.

03:08 The clinical exam though has multiple abnormalities.

03:11 You have left eye convergent strabismus, that's a misalignment of the eyes.

03:15 He has no pupillary reflex in the left eye.

03:19 He has a white retina in fundoscopy, which you can see in the image and the right eye is told to be normal.

03:27 Now there are also paraclinical examinations and these are significant for no visual evoked potentials in the left eye and the MRI of the orbits reveals a retina-derived tumor with spread to the intrabulbar part of the optic nerve and with vitreous seeding that is floating tumor cells.

03:49 Now, a common child tumor that has this clinical presentation is retinoblastoma.

03:57 So then the diagnosis there is unilateral left eye retinoblastoma.

04:03 So the next part becomes to figure out, well, how do we manage it? What should we do? And that depends very much on how advanced and involved the retinoblastoma is So what we need to do here when we're trying to treat these patients with retinoblastoma is we wanna preserve the child's life.

04:22 We want to obviously preserve also the child's vision and minimize side effects.

04:27 Now this patient, unfortunately, has advanced disease.

04:30 He has spread it to the intrabulbar portion of the optic nerve and he even has vitreous seeding.

04:36 Now, the risk here is further progression and eventual risk of his life.

04:40 So the eye though is already significantly impaired.

04:45 He has no visual evoked potentials, which means there's no conduction through the optic nerve.

04:50 That eye does not work at all.

04:52 So really, given how severe and advance his case is, the best result is achieved by removal of all of the affected structures.

05:02 That is eye enucleation to reduce the risk of any spread of the retinoblastoma, given that the eye is already completely damaged.

05:10 So again, the answer choice is answer choice C, eye enucleation.

05:14 Now, let's go through the answer choices a bit more to talk about them in more detail.

05:19 Now we're told -- okay, that this patient's presenting with a sporadic unilateral retinoblastoma and I said sporadic because there's no family history.

05:28 And it has impairment of his eye function with signs of disease spread so we concluded, given that there is severe disease, enucleation is the best possible treatment for this patient.

05:42 And that's what USMLE is doing these days.

05:44 There's no blanket treatments anymore.

05:47 They want you to pay attention to the clinical case being presented and figure out, of the various treatment options, what's the best one for this patient.

05:57 Now, retinoblastoma is the most frequent intraocular malignancy of childhood and it's caused by mutations in the gene RB.

06:07 Now the RB protein is a cell cycle regulator which suppresses the transition of a cell from G1 to S-phase of the cellular cycle and the mutation can be sporadic, as in this child given no positive family history or inherited.

06:23 Now, inherited retinoblastomas or inherited in an autosomal dominant fashion.

06:30 So then, 50% of the offspring of a person who had retinoblastoma will have a mutant RB gene.

06:37 Now both alleles should be non-functional in order for the disease to develop.

06:43 That means in the case of an inheriditary retinoblastoma, the second mutation has to occur on its own since only one non-function allele is inherited.

06:54 Now in the case a sporadic disease, you need two consecutive sporadic mutation in the RB gene to get the same disease.

07:03 Now the main clinical signs of retinoblastoma include the following: abnormal white reflection of the pupil, also called a cat-eye reflex because if you shine in a light in the cat's eye, it'll look white.

07:16 If you take a photograph with flash on a human, it will be red so we call it a cat eye reflex because instead of it being normally red, it's white.

07:24 That's caused by the white appearance of the tumor on the fundus.

07:28 You will also have strabismus usually converging due to the occupation of the part of the retina where the macula is located.

07:36 You can have a loss of vision. In advance stages, you'll have a retinal detachment, proptosis, and nystagmus.

07:43 Now looking at the other answer choices, answer choice E, brachytherapy.

07:47 This is a type of radiotherapy in which a radioactive agent is implanted under the sclera close to the tumor.

07:55 Now this is suitable for small tumors located far from the optic nerve or macula but in this child, the tumor involves the macula and has shown signs of spread so this would not be appropriate.

08:07 Answer choice B which is chemotherapy is an effective method of treatment using cases of eye sparing is reasonable.

08:16 Still, there are some, of course, systemic side effects to chemo but in this case, the eye function is lost.

08:22 There is no sparing of function and enucleation is a safer choice.

08:26 Now answer choice D, cryotherapy -- now a cryoprobe is cooled by nitrous oxide and is actually applied to trans scleral to destroy a tumor in underlying choroid.

08:40 Now cryotherapy is best in use in the treatment of the disease, exclusively confined to the retina.

08:47 While in this case, there's actually spread with vitreous seeding so the spread even goes to the optic nerve and thus, a cryotherapy would not be appropriate.

08:57 Answer choice E, laser coagulation -- this is used for small tumors or residual recurring tumors after chemotherapy but again in this case, the child's tumor's too large and progressed, it would not be appropriate.

09:10 So now let's review some high-yield facts for retinoblastoma.

09:14 Now, retinoblastoma is a cancer of the immature cells of the retina.

09:19 It's the most common intraocular tumor of childhood and the diagnose is nearly always occurs at a young age.

09:26 Now, there are hereditary and sporadic forms and the hereditary is autosomal dominant and there's roughly a 50-50 split between the prevalence of both.

09:37 Now, the genes implicated in their hereditary form are RB1 and MYCN.

09:43 Now common signs and symptoms are leukocoria, deterioration of vision, glaucoma, and strabismus.

09:51 And the treatment depends on the type and staging of tumor.

09:55 Eye enucleation is generally for unilateral tumors that are present with advanced-staged disease.

10:01 You can have external beam therapy.

10:04 You can have brachytherapy, cryotherapy, chemotherapy, and laser coagulation therapies.

10:10 Now, I'd like you to refer to the image here of a patient's eye in which the left eye shows leukocoria and this is what you will see -- they can show a similar picture on USMLE.

10:21 In which the patient's left eye shows leukocoria or it's white due to the tumor and it's commonly going to be seen with retinoblastoma.