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Clinical case: Oculomotor nerve palsy and distal myopathy - want to learn more about it?

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Clinical case: Oculomotor nerve palsy and distal myopathy

In this article, we describe a case of a woman who presented with decreased vision, pathological ophthalmoscopic examination, limb paresis, and nervous system lesions. Her final diagnosis is neurofibromatosis type 2 (which caused an oculomotor nerve palsy). Do you want to find out more about it? Stick around to see how the diagnosis was reached, the clinical presentation, and the relevant anatomy.

Key facts
Extraocular muscles Levator palpebrae superioris (elevation of the superior eyelid), superior oblique (outward and downward movement of the eye), superior rectus, medial rectus, lateral rectus, inferior rectus (movements of the eye in the four respective directions, inferior oblique (eye elevation and abduction)
Optic disc swelling An increase in fluid within or surrounding the axons of the optic nerve, seen in ophthalmoscopy.
Hydrocephalus A condition in which there is an excessive accumulation of cerebrospinal fluid (CSF) within the brain.
Tonsillar herniation A condition during which the cerebellar tonsils are displaced inferiorly through the foramen magnum, resulting in compression of the lower brainstem and upper cervical spinal cord.
Cavernous sinus contents Internal carotid artery, oculomotor never, trochlear nerve, ophthalmic nerve, maxillary nerve, abducens nerve.

After reviewing this case you should be able to describe the following:

  • The attachments, function and innervation of the extraocular muscles, especially as they relate to this case.
  • What is meant anatomically by “optic disc swelling;” The clinical significance is of this condition.
  • What is the difference between communicating and non-communicating hydrocephalus, and how they are typically differentiated radiologically.
  • What is meant anatomically by “tonsillar herniation;” the clinical significance of this condition.
  • The locations and contents of the cavernous sinus, and how compression of the sinus could result in some of the ocular signs and symptoms discussed in this case.

This article is based on a case report published in the Journal "Case Reports in Surgery" in 2015, by Caroline C. Jadlowiec, Beata E. Lobel, Namita Akolkar, Michael D. Bourque, Thomas J. Devers, and David W. McFadden.

Case description

History

The patient was a 23-year-old Malay woman who presented with an eight-year history of drooping of her left eyelid and limited upward movement of that eye. Her right eye had a 20-year history of poor vision and progressive outward deviation. She also had progressive right lower and upper limb paresis that manifested in walking difficulties. The weakness in the upper and lower limbs initially involved the distal muscles, but currently involves both proximal and distal muscles. The patient reported that she has noticed a change in her voice, and a right-sided hearing disturbance for the past two years.

Physical examination

Upon examination, there was mild eyelid retraction in the right eye with exotropia (outward deviation) and hypertropia (upward deviation), whereas the left eye showed mild ptosis (Figure 1).

Figure 1. Photograph of the patient’s eyes showing right exotropia and hypertropia, and left ptosis.

Both pupils were normal in size. The patient had bilateral posterior subcapsular cataracts (cloudiness of posterior surface of lens) and generalized optic disc swelling, with slightly tortuous vessels (Figure 2).

Figure 2. Ophthalmoscopic images of patient showing swollen optic discs and a macular scar on right eye.

A few pedunculated cutaneous lesions were noticed over her body and scalp (Figure 3) and her right thigh had some cafe au lait spots (hyperpigmented skin regions that are usually associated with neurofibromatosis). The patient also had sensorineural deafness and right vocal cord paralysis.

Figure 3. Skin lesion.

Imaging

MRI showed bilateral acoustic and trigeminal schwannomas with multiple additional tumors (Figure 4).

Figure 4. Contrast enhanced T1 MRI images (A, sagittal, B, axial, coronal) showing multiple enhancing tumors in much of the lower brain and cerebellum. There also is enhancement within the cavernous sinus (B). Also, lateral ventricles are enlarged, indicating obstructive (non-communicating) hydrocephalus (C).

There were also intraspinal lesions and peripheral nerve lesions, likely meningiomas or neurofibromas. Obstructive hydrocephalus resulting in tonsillar herniation was noted.

Diagnosis

The patient was diagnosed with neurofibromatosis type 2 with skin, eye, and neural involvement. Craniotomy and tumor debulking by neurosurgical team were planned for this patient, but she declined treatment.

Medical and anatomical considerations

Neurofibromatosis type 2

Neurofibromatosis type 2 is an autosomal dominant disease caused by a mutation in chromosome 22 band q 11- 13.1, called the NF2 gene (neurofibromin 2), which codes for the merlin protein (moesin-ezrin-radixin-like protein). Neurofibromatosis type 2 generally presents with VIIIth nerve symptoms such as hearing loss, tinnitus, and disequilibrium due to vestibular schwannoma, meningioma, glioma, and ependymoma. Pediatric cases are generally diagnosed early by the appearance of skin-related tumors (cafe au lait spots). The most common ocular finding is subcapsular cataract, which was present in our patient. The patient in this case initially had third nerve palsy and only later developed VIIIth nerve symptoms. This is the reverse of typical cases.

Figure 5. Dissection image of the skull base structures, highlighting the cavernous sinus region.

This patient likely had an oculomotor nerve schwannoma or an expansive process in the temporal region close to the cavernous sinus that likely compressed the nerve. The latter is actually more likely than the former because her MRI showed involvement of both cavernous sinuses (Figure 4). Mass effect to the medulla within the foramen magnum (as may have occurred in this patient due to the hydrocephalus) may compress its contents, including the glossopharyngeal, vagus, and spinal root of accessory nerve. However, because of the selective and limited involvement of the recurrent laryngeal nerve in this case, hydrocephalus resulting in nerve compression seems unlikely. Rather, the authors of the case postulated that the right vocal cord palsy was due to a small schwannoma to the vagus nerve somewhere along its course or perhaps directly on the recurrent laryngeal nerve, which may not have been obvious on imaging. Furthermore, peripheral schwannomas, meningiomas, and neurofibromas may cause weakness and numbness, which can progress to hand and foot drop.

Because neurofibromatosis type 2 is an autosomal dominant disease with significant morbidity, patients with family history of neurofibromatosis type 2 should be screened to detect the disease in the early stages, before irreversible damage occurs. Early presentation and intervention, ideally before multiple cranial nerves are involved, will result in a reasonable prognosis for this condition. 

Pupil Size & Light Reflex

The limbs muscle wasting and walking difficulties suggest some of the numerous brain tumors were impinging on brain and/or spinal motor control centers (note also cerebellar involvement in Figure 4). The normal pupil size in this patient suggests that the light reflex is intact meaning that the autonomic fibers that control the pupillary muscles are functioning normally. The parasympathetic fibers that diminish the size of the pupils are part of the oculomotor nerve whereas the dilator pupillae muscle is innervated by sympathetic fibers that arise from the superior cervical ganglion and typically enter the orbit with the nasociliary branch of the ophthalmic nerve.

Recommended video: Eyeball
Structure of the eyeball seen in a transverse section.

Finally, although the authors of this case made reasonable conclusions as to the likely compressive effects of tumors on individual nerves, the presence of multiple tumors throughout the brain and brainstem does not allow the ruling out that some of the observed signs were due to upper rather than lower motor neuron injury.

Explanations of objectives

Objectives

  • The attachments, function and innervation of the extraocular muscles, especially as they relate to this case.
  • What is meant anatomically by “optic disc swelling;” The clinical significance is of this condition.
  • What is the difference between communicating and non-communicating hydrocephalus, and how they are typically differentiated radiologically.
  • What is meant anatomically by “tonsillar herniation;” the clinical significance of this condition.
  • The locations and contents of the cavernous sinus, and how compression of the sinus could result in some of the ocular signs and symptoms discussed in this case.

Extraocular muscles

This patient showed left ptosis, which suggests some paresis of the left levator palpebrae muscle and accordingly compromised function in the left oculomotor nerve (and its contained sympathetic fibers; cf. below). The patient also showed right hypertropia and exotropia, suggesting paresis in the inferior and medial recti muscles and compromised function in the right oculomotor nerve. More details on the extraocular muscles are presented directly below (see also Figure 5):

  • Levator palpebrae superioris: originates from roof of orbit immediately anterior to optic canal - passes forward covering superior rectus - tendon passes into upper lid to attach to superior tarsus and ski; arising from the inferior surface of this muscle is a layer of visceral muscle known as the superior tarsal muscle, which also inserts into the tarsus (the tarsus is a layer of thickened connective tissue within the lids that maintains their shapes); somatic part of the muscle is innervated by superior division of oculomotor nerve and visceral part by sympathetic system; muscle raises upper eyelid; paralysis of smooth muscle results in upper lid drooping (ptosis can involve one or both parts of the muscle); total paralysis results in the inability to open the eye voluntarily.
  • Superior Oblique: originates from posterior aspect of roof of orbit and becomes tendinous before reaching the front of orbit; at superior medial corner of front of orbit tendon is attached to the frontal bone by a fibrocartilaginous pulley (trochlea); at the trochlea the tendon turns sharply posteriorly, inferiorly and laterally, deep to the superior rectus to inserts lateral to and in the upper lateral quadrant of the posterior surface of the eyeball; innervated by trochlear nerve; acts to move eye outward and downward; also intorsion (testing the action of this muscle is counterintuitive; the patient is asked to look down and in; this is because only the superior oblique can perform this function).
  • Superior, medial, lateral, inferior recti: all originate from annulus tendineus and all insert on the respective anterior quadrant of the eyeball; all are innervated by oculomotor nerve except lateral rectus, which is innervated by abducent nerve; superior rectus elevates and intorts eye whereas inferior rectus depresses and extorts eye; both also cause some adduction; medial rectus adducts eye whereas lateral rectus abducts eye.
  • Inferior Oblique: originates from floor of orbit; inserts into lower lateral quadrant of posterior surface of eyeball, below insertion of superior oblique; elevates eye and causes abduction, also extorsion.

Figure 6. Dissection image of left orbit (eyeball removed) highlighting the extraocular muscles. 

Optic disk swelling

The optic disc or optic nerve head is the point of exit for retinal axons exiting the eye. Because there are not any rods or cones overlying the optic disc, this spot corresponds to a small blind area in each visual field. Optic disc swelling (edema) refers to the swelling as seen with an ophthalmoscope that is associated with an increase in fluid within or surrounding the axons of the optic nerve (Figure 2). While unilateral disc edema is more common, bilateral disc edema can occur.

Papilledema is a common form of optic swelling that results from increased intracranial pressure. In this patient, the presence of the tumors in her brain (and especially those that could be exerting pressure on the cavernous sinus) could explain the appearance of the swollen discs, which, in her case, could also have been referred to as papilledema.

Figure 7. Optic disc.

Hydrocephalus

Hydrocephalus is a condition in which there is an excessive accumulation of cerebrospinal fluid (CSF) within the brain. Hydrocephalus can occur congenitally or be acquired. There are two primary types of hydrocephalus: communicating and non-communicating. Diagnosis is typically made by examination (increased CSF pressure) and medical imaging.

Figure 8. Ventricles of the brain.

Communicating hydrocephalus (non-obstructive) is caused by impaired cerebrospinal fluid reabsorption presumably associated with functional impairment of the arachnoid granulations. Non-communicating (obstructive) hydrocephalus (Figures 4&8&9) is caused by a CSF-flow obstruction generally leading to dilation of one or both lateral ventricles, which provides radiological evidence for obstructive rather than non-obstructive hydrocephalus. 

Figure 9. T2 MRI of a patient (not patient in this case) showing very enlarged lateral ventricles, which is consistent with obstructive hydrocephalus.

Tonsillar herniation

In tonsillar herniation (downward cerebellar herniation, transforaminal herniation, "coning"), the cerebellar tonsils are displaced inferiorly through the foramen magnum resulting in compression of the lower brainstem and upper cervical spinal cord (Figure 10). This pressure on the brainstem can result in dysfunction of the primary neural structures controlling respiratory and cardiac function, eventually resulting in death.

Figure 10. Sagittal T1 skull and brain MRI showing level of foramen magnum (dashed circle) and location of cerebellar tonsil (highlighted with green).

Cavernous sinus

The cavernous sinus is a dural venous sinus that is located on the left and right sides of the sella turcica (Figures 4B). The sinus receives blood from the superior and inferior ophthalmic veins through the superior orbital fissure and from superficial cortical veins, and has connections to the basilar plexus of veins posteriorly. The ICA (carotid siphon), and cranial nerves III, IV, V1, V2 and VI all pass through this blood filled space.

The cavernous sinus drains via the superior and inferior petrosal sinuses, ultimately into the internal jugular vein via the sigmoid sinus. Because the superior and inferior ophthalmic veins drain into the sinus, any increases in pressure in the sinus (as likely caused by a tumor in this case) will impede venous drainage from the eye and orbit. This will result in papilledema and also can cause exophthalmos (protruding eye). And, similarly, compression of the sinus can result in nerve compression (e.g., oculomotor nerve), which will manifest in extraocular muscle weakness, as found in this patient.

Clinical case: Oculomotor nerve palsy and distal myopathy - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 1,134,051 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

Reference:

  • Tevaraj JMP, Li Min ET, Noor RAM, Yaakub A, Wan Hitam WH. Neurofibromatosis Type 2 Presenting with Oculomotor Ophthalmoplegia and Distal Myopathy. Case Reports in Ophthalmological Medicine Volume 2016, Article ID 1701509, 3 pages. 
  • Modified by Joel A. Vilensky PhD , Carlos A. Suárez-Quian PhD , Aykut Üren, MD.

Authors:

  • Joel A. Vilensky 
  • Carlos A. Suárez-Quian
  • Aykut Üren

Layout:

  • Abdulmalek Albakkar
  • Adrian Rad

Illustrations:

  • Ventricles of the brain - lateral-left view - Paul Kim
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

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