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  1. EOM actions 

  2. Cong hypothyroidsim

EXTRAOCULAR MUSCLE ACTIONS

 The actions of extraocular muscles can be asked in any PG Entrance exam. It is a straightforward question and can be answered in 10 seconds.

 BASIC CONCEPTS

Primary action: is the action when the eye is in the primary position.

(Primary position means when the eye is  looking straight ahead at  fixed point on the horizon with the head erect)

Subsidiary action: are the additional effects on the position of the eye.

 NOW

Horizontal recti have only one action (i.e primary action only)

Medical rectus: Adduction

Lateral rectus: Abduction

 AND

All other muscles have one primary and two subsidiary actions.

 AND

Primary action of oblique muscles is torsion.(intorsion or extorsion).

 AND

Primary action of superior rectus is elevation and inferior rectus is depression.

 HOPE THE ABOVE STUFF MADE SENSE

OK, EVEN IF IT DIDN’T

JUST Remember the mnemonic “SINRAD” which means

All Superiors are INtortors

All Recti (obviously I am talking about only the 2 vertical recti) are ADductors.

 {The mnemonic also implies (inferiors are extortors and obliques are abductors) – but u don’t need to remember this}.

 With the above knowledge read the below table once

 

Primary

Subsidiary actions

Medial rectus

Adduction

------------

Lateral rectus

Abduction

------------

Superior rectus

Elevation

Intorsion and Adduction

Inferior rectus

Depression

Extorsion and Adduction

Superior oblique

Intorsion

Depression and Abduction

Inferior oblique

Extorsion

Elevation and Abduction

 Now take a paper and write down the actions once without looking.

IT WORKS. And u won’t forget even if u want to….J.

PS: For all the doubters around, I have verified the table in Parsons’ 19 edn (424).

 

CONGENITAL HYPOTHYROIDISM

 Etiology

The commonest causes include:

·         thyroid dysgenesis (80-90%)

·         ectopic thyroid or hypoplastic thyroid as a result of a failure of normal descent of the thyroid in development

 More rarely congenital hypothyroidism may result from:

·         panhypopituitarism - note that this form will not be detected by neonatal screening, since this detects a high TSH in response to a low thyroxine level

·         inborn errors of metabolism of the thyroid

·         maternal ingestion of goitrogens or other drugs after the eighth week of gestation

 There is an association with Down's syndrome.

 “Note”: most newborns are asymptomatic due to the transplacental passage of moderate amounts of maternal T4 (can produce levels in the fetus 25-50% of normal)

 Clinical Features

  1. MC in girls
  2. prolonged neonatal jaundice (OFTEN THE EARLIEST SIGN)
  3. coarse facies, with macroglossia
  4. dry skin
  5. hoarse cry
  6. hypotonia
  7. hypothermia
  8. umbilical hernia
  9. constipation
  10. presence of a goitre suggests a goitrogen aetiology
  11. the posterior fontanelle remains open, and closure of the anterior fontanelle is delayed
  12. the infant may be anaemic
  13. if untreated mental retardation may develop
  14. Congenital heart disease is the most common congenital abnormality, especially pulmonary stenosis, ASD, and VSD.

 Investigations

1. Screening

·         All neonates are screened at 48 hours for TSH (and/or T4) from a blood drop placed on filter paper (avoids the TSH surge at birth due to stress producing false positive results)

·         Screens for primary hypothyroidism (does not detect pituitary cause)

·         if result is <0.20 mIU/L – see patient immediately for history/physical, to draw a stat serum T4 and TSH, and to start thyroid hormone therapy (see below)

 Low birth weight babies

·         In very low birth weight babies (particularly premature neonates) TSH screening should be repeated a at two weks after birth to detect those babies where immaturity of the hypothalamic-pituitary-thyroid axis may initially mask primary congenital hypothyroidism.

 2. Serum

·         Elevated TSH and reduced T4

·         Anemia

·         unconjugated hyperbilirubinemia

 3. Imaging Studies

 à Radionuclide Scintigraphy (thyroid scan)

·         Radioactive technetium to detect developmental defects of the thyroid (i.e., dysgenesis, ectopia, etc.)

 à Skeletal X-Rays

·         for baseline bone age (BONE AGE < CHRONOLOGICAL AGE)

·         retardation of osseous development

·         absence of distal femoral epiphysis

·         epiphyses with multiple foci or ossification (epiphyseal dysgenesis)

·         deformity ("beaking") of the 12th thoracic or 1st or 2nd lumbar vertebrae

 à Skull X-Rays

·         large anterior and posterior fontanelle

·         Wide sutures

·         wormian bones

·         enlarged sella turcia +/- erosion and thinning

 à 2D Echo

·         cardiomegaly +/- pericardial effusion

 à ECG

·         low voltage P, QRS, T waves

 MANAGEMENT

 1. Thyroid Replacement

1. Initial

·         Begin with positive screen as the test results are returned in 10 days and thus the infant has been untreated for this period

·         Start thyroid hormone at 6 microg/kg po od

·         Arrange for bone age and radionuclide scan

2. Maintenance

·         See initially at 3 and 6 months of age then q6m

·         Monitor TSH, T4 levels, growth parameters, clinically

·         Monitor bone age q1y to ensure adequate osseous development (will be delayed with undertreatment)

·         Full developmental assessment (with hearing tests) at 8-9 months of age and at school entry

·         Long term follow-up is required as this is a chronic life-long disorder

 2. Prognosis

·         Normal growth, intelligence, and life span if detected within the first few weeks of life

·         Short stature, mental retardation, progressive ataxia and delayed puberty with delays in detection.  

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