Unusual presentation of idiopathic intracranial hypertension

Abstract

Idiopathic intracranial hypertension typically presents with holocephalic headache associated with nausea, vomiting and bilateral papilledema. Involvement of the sixth cranial nerve is relatively common. The involvement of other cranial nerves, however, is rare in this disorder. We describe a patient with idiopathic intracranial hypertension who presented with episodic unilateral retro-orbital pain and multiple cranial nerve abnormalities without papilledema. Imaging studies excluded alternate diagnoses, and the immediate resolution of symptoms after lumbar puncture confirmed that these symptoms were due to intracranial hypertension. Atypical presentations of such a disabling yet treatable disorder is very important to recognise and address.

Background

The annual incidence of idiopathic intracranial hypertension is 0.9 per 100 000.¹ This incidence increases in obese women between 15 and 44 years old up to 3.3 per 100 000.¹ Recent weight gain may be a risk factor for increased intracranial hypertension. Although the underlying aetiology is idiopathic, conditions associated with intracranial hypertension include tetracycline use, hypervitaminosis A and growth hormone use.^{2 3}

Different mechanisms have been proposed to explain the pathogenesis of intracranial hypertension; however, the precise mechanism remains unknown. The typical clinical presentation of idiopathic intracranial hypertension is headache, transient visual obscurations, tinnitus and double vision.⁴ Permanent visual loss is the major morbidity associated with idiopathic increased intracranial hypertension. Severe visual loss was found in 6%–14% of patients.^{1 5}

Case presentation

A 43-year-old man presented with a history of episodic pain around the right eye. The pain started about 5–6 weeks before admission and was described as pressure-like with severity 7/10. The pain lasted about 10 min and then resolved, with episodes three to four times per day. The pain did not wake the patient from sleep and lacked positional exacerbation. The patient denied any precipitating factors. There was no associated conjunctival congestion, red eye, lacrimation, ptosis or facial sweating. The patient did not notice and trigger points.

Two days prior to his presentation, the patient reported that his pain worsened and became continuous. The pain remained behind the right eye with 7/10 severity. At times, the pain became severe at 10/10 for periods of about 10 s. The patient also endorsed binocular diplopia over the 2 days prior to presentation, which resolved when he closed one eye.

The patient denied any change in speech, visual acuity, balance, sensation or strength. He denied tinnitus, hearing loss, photophobia, phonophobia, nausea or vomiting.

The patient had a recent history of antibiotic for respiratory tract infection, and a recent CT chest revealed bronchiectasis. He endorsed a history of recent weight gain of about 18 kg over the past few months.

Additional prior medical history included sinus polyps, hypertension, diabetes, obesity and tobacco use. His family history included lymphoma, pancreatic cancer and oesophageal cancer.

On general physical examination, the patient appeared obese but healthy with no abnormalities noted on cardiovascular, respiratory and abdominal examination.

On neurologic examination, the evaluation of his cranial nerves revealed slight asymmetry in pupillary size, with right pupil 2 mm, and left pupil 3 mm, briskly reactive bilaterally. The visual fields were normal. Funduscopy was normal, with flat optic discs with sharp disc margins. The patient endorsed double vision in all directions of gaze with the second image next to the first. His diplopia was worse on rightward gaze. Both eyes were slightly restricted in abduction. The patient could not completely converge the eyes. Vertical eye movements were normal, so Bielschowsky manoeuvre was not done. No nystagmus was evident. Facial sensation was asymmetric, with decreased sensation in the right V1 distribution. However, corneal reflex was normal bilaterally. Facial movement was full and symmetric. The palate elevated symmetrically, shoulder shrug strength was normal and the tongue protruded midline.

The remainder of his neurologic examination was normal, including supple neck without meningismus, normal attention and language, normal strength, sensation and reflexes throughout the upper and lower extremities.

Investigations

CT head without contrast was unremarkable.

CT angiography of the head and neck showed normal arteries of the head and neck with no occlusions or dissection and no signs of cerebral venous thrombosis. The optic nerve sheaths appeared distended (figure 1A).

Figure 1.

(A) CT angiography, sagittal view, showing optic nerve sheath expansion. (B) MRI orbit, T2 axial view. (C) MRI orbit, T1 coronal view with gadolinium, showing the enlargement of the optic nerve sheath. (D) MRI orbit, T2 coronal view.

MRI of the brain and orbits showed a partially empty sella and optic sheaths which were dilated to 8 mm, which suggested increased intracranial pressure (figure 1B–D). The brain parenchyma appeared normal. Cavernous sinus and superior orbital fissure were normal.

Lumbar puncture (LP) was performed and showed an opening pressure of 29 cm H₂O. Cerebral spinal fluid (CSF) analysis showed no white blood cells, normal protein and glucose levels. Further CSF studies included Venereal Disease Research Laboratory (VDRL)/Rapid Plasma Reagin (RPR), oligoclonal-bands, IgG synthesis rate and index, ACE, fungal stain, cryptococcus antigen, cytology and cytometry which were all negative.

Differential diagnosis

Due to the progressive nature of the symptoms, the possibility of infection, neoplasm and inflammation were considered. His recent history of respiratory tract infection with bronchiectasis raised concern for infection. Intracranial neoplasm was considered due to his family history of multiple family members affected by malignancy. Because of his history of extensive sinus polyps, inflammatory conditions such as Tolosa-Hunt syndrome or Gradenigo syndrome were considered as well.

Other primary types of headache were considered, including migraine, trigeminal neuralgia, cluster headache and paroxysmal continue; however, the headache characteristics and other findings on the neurological examination did not support any of these diagnoses. In addition, none of these diagnoses is known to be associated with increased opening pressure on LP.

Diabetic cranial neuropathy can cause different cranial neuropathy. However, pupil involvement is not in diabetic neuropathy, the involvement of multiple cranial nerves at the same time is not very rare. Also, diabetic cranial neuropathy is not known to be associated with elevated opening pressure on LP.

Ultimately, the patient symptoms of headache with double vision in the setting of recent weight gain raised a strong suspicion for increased intracranial pressure as the aetiology of his symptoms. His imaging (figure 1) supported this suspicion. LP provided a diagnostic confirmation of intracranial hypertension, as the opening pressure was raised to 29 cm H2O. Additionally, the patient received a therapeutic benefit from LP, with complete resolution of his headache and diplopia; cranial nerves examination was normal after the LP, including pupillary asymmetry and facial sensory deficits. The opening pressure maybe slightly elevated in obese patients but without affecting the cranial nerves.

Treatment

The patient’s symptoms completely resolved, his examination was normal after the LP, and he was started on acetazolamide 500 mg two times per day. The morning after his LP, the patient reported that his headache and diplopia were returning, though to a lesser degree. His dose of acetazolamide was increased to 750 mg two times per day with improvement in his symptoms.

Outcome and follow-up

At a follow-up appointment with his primary care physician 1 week later, the patient reported that he had only a mild residual headache but persistent diplopia. Neurological examination including cranial nerves examination was normal, at that time. The patient was started on topiramate. This helped decrease the patient headache. Topiramate has been used as a treatment in idiopathic intracranial hypertension. However, it cannot be ruled out that the patient had an associated migraine component.

After 2 weeks, on a phone call follow-up, the patient’s headache had completely resolved, and his diplopia was present only with extreme rightward gaze. Acetazolamide was increased to 1000 mg two times per day, at which time he had full resolution of the residual diplopia with no adverse drug effects.

On 3 months clinic follow-up visit, the patient was completely asymptomatic with no side effects on the treatment applied.

Discussion

Although headache is the most common presenting symptom of idiopathic intracranial hypertension, the characteristic of headache is not specific to idiopathic intracranial hypertension. Patients can present with different types of headaches, including general headache, unilateral and retro bulbar, which may or may not be related to posture.⁶ In addition, the diagnosis of idiopathic intracranial hypertension gives the impression of gradually worsening headache, with continuous pain. Many patients present with intermittent headache, with a duration of 1 hour or more.^{4 6} However, disability is uncommon for patients who present with headaches of short duration.

Papilledema is another characteristic finding in idiopathic intracranial hypertension; however, patients may be diagnosed with idiopathic intracranial hypertension without papilledema.⁷ This difference is related to anatomical differences or other factors affecting the optic nerve itself.⁸

The criteria for a definitive diagnosis of idiopathic intracranial hypertension are as follows: papilledema, normal neurological examination except for cranial nerve abnormalities, and neuroimaging without evidence of intracranial lesion or abnormal meningeal enhancement, and LP showing normal CSF composition and elevated opening pressure ≥25 cm H2O for adults or ≥28 cm H2O in children. If a patient does not have papilledema, the diagnosis can still be made if the patient meets all other criteria and also has unilateral or bilateral abducens nerve palsy.⁹

Abducens nerve palsy is a known complication of idiopathic intracranial hypertension.⁴ However, other cranial nerves involvement is very rare. Trigeminal nerve involvement has been previously described, with nerve palsy attributed to increased intracranial pressure.¹⁰

The patient described above also exhibited signs of partial oculomotor nerve involvement, exhibited by the pupillary asymmetry. A few case reports have described this finding as a rare complication of idiopathic intracranial hypertension.^{11 12} The exact mechanism of this involvement is not clear; however, physical pressure caused by the increased intracranial pressure could be a possible mechanism. Another possible explanation could be the remarkable increase of the optic nerve sheath diameter (figure 1C, D). This may cause crowding in the retro bulbar area resulting in pressure on the other nerves including the oculomotor nerve, abducens nerve and the frontal nerve, a division of V1 from the trigeminal nerve. All these nerves enter the orbit through the superior orbital fissure, where they are in close proximity with the optic nerve (figure 2).¹³

Figure 2.

Orbital apex (diagram). Case courtesy of Dr Craig Hacking, Radiopaedia.org, rID: 52363.

Learning points.

• Headache in idiopathic intracranial hypertension may be unilateral, retro bulbar and have different characteristics.

• Idiopathic intracranial hypertension may present without papilledema. However, this does not mean the absence of visual symptoms, including blurry vision episodes.

• Besides the abducens nerve, other cranial nerves may be affected by increased intracranial pressure, such as oculomotor and trigeminal nerves.