[vc_row row_type=”row” use_row_as_full_screen_section=”no” type=”full_width” oblique_section=”no” text_align=”left” css_animation=””][vc_column][ultimate_heading main_heading=”Candidate brief” main_heading_color=”#000000″ sub_heading_color=”#000000″ main_heading_style=”font-weight:bold;” main_heading_font_size=”desktop:36px;”]

“This patient has complained of double vision.  Please examine their eyes.”

[/ultimate_heading][vc_empty_space image_repeat=”no-repeat”][vc_video link=”https://vimeo.com/149972951″][vc_empty_space image_repeat=”no-repeat”][vc_row_inner row_type=”row” type=”full_width” use_row_as_full_screen_section_slide=”no” text_align=”left” css_animation=””][vc_column_inner width=”1/4″][stat_counter icon_size=”32″ counter_title=”Station Time” counter_value=”20″ counter_suffix=” minutes” speed=”3″][/vc_column_inner][vc_column_inner width=”1/4″][stat_counter icon_size=”32″ counter_title=”Time for this encounter” counter_value=”10″ counter_suffix=” minutes” speed=”3″][/vc_column_inner][vc_column_inner width=”1/4″][stat_counter icon_size=”32″ counter_title=”Maximum time to examine your patient” counter_value=”6″ counter_suffix=” minutes” speed=”3″][/vc_column_inner][vc_column_inner width=”1/4″][stat_counter icon_size=”32″ counter_title=”Minimum time for discussion and questions” counter_value=”4″ counter_suffix=” minutes” speed=”3″][/vc_column_inner][/vc_row_inner][vc_empty_space image_repeat=”no-repeat”][/vc_column][/vc_row][vc_row row_type=”row” use_row_as_full_screen_section=”no” type=”full_width” oblique_section=”no” text_align=”left” css_animation=””][vc_column][vc_accordion style=”accordion”][vc_accordion_tab title=”Common examiner questions”][vc_column_text]Common examiner questions include the following:

  1. What do you think this patient has?
  2. How would you like to investigate this patient next?
  3. What do you think the underlying cause of this patient’s signs is?

[/vc_column_text][/vc_accordion_tab][vc_accordion_tab title=”Diagnosis and clinical signs”][vc_column_text]This patient has a IVth cranial nerve palsy.  This is the cranial nerve palsy that affects eye movements that is most subtle, and may be overlooked if you are in a rush.[/vc_column_text][/vc_accordion_tab][vc_accordion_tab title=”Discussion”][vc_column_text]

Clinical Picture:

Superior oblique of the eye derives its innervation from the fourth cranial nerve, also known as the trochlear nerve. The functions of the superior oblique muscles are depression, in-torsion and abduction of the eyeball. Hence, a patient with fourth nerve palsy will, predominantly, complain of vertical diplopia –usually worse on downward gaze –and torsional diplopia.

Another important characteristic of the fourth nerve cranial palsy is the development of head tilt. This is usually to reduce the diplopia through picture alignment. The tilt is commonly seen opposite to the lesion. A paradoxical head tilt, is seen in a minority of patients who tilt their heads ipsilateral to the diseased eye, results in a wider separation of the images and, subsequently, disregarding one of the formed images.

Initial Investigation:

The ocular exam will usually not be helpful in localization of the problem. Investigations like Maddox rod test, also known as the cover uncover test and the Parks-Bielschowsky 3-step test are usually employed to correctly localize the problem.

The 3-step test, best in determining vertical strabismus, includes the following steps:

  • Determining the side of hypertropia in the primary gaze.
  • Subsequently concluding whether the hypertropia is worse on left or right gaze.
  • Finally, determining the head tilt that exhibits greater hypertropia.

The Maddox rod test is helpful in measuring excyclotorsion.

Underlying Pathology:

Fourth nerve palsy can be can be congenital or acquired. Congenital type is thought to arise due to developmental issues in the nucleus or the maldevelopment of the nerve or muscle and even the tendon. Paediatric patients may present with facial asymmetry and torticollis. Acquired cases are most often idiopathic but can arise in the setting of a head trauma. Systemic diseases like thyroid dysfunction and multiple sclerosis can also result in palsy as can tumours and vascular malformations compressing the nerve.

Additionally, bilateral nerve palsy should always be considered in cases where unilateral palsy is present.

Treatment:

Surgical intervention is usually indicated for long standing cases. Botulinum toxin, a neurotoxic protein which blocks neurotransmitter release in the muscles, is used, however its use is greatly discouraged. Surgery may be used to weaken the antagonist muscles, to lessen the exertion and correct the strabismus.[/vc_column_text][/vc_accordion_tab][vc_accordion_tab title=”Specimen case presentation”][vc_column_text]”This patient has a left IVth cranial nerve palsy.  I would like to complete my examination by examining the other cranial nerves and the rest of the neurological system.”[/vc_column_text][/vc_accordion_tab][/vc_accordion][/vc_column][/vc_row]