Reversal of Imaging Findings of Idiopathic Intracranial Hypertension After Lumbar Puncture

< Idiopathic intracranial hypertension >

• Idiopathic intracranial hypertension (IIH) is characterized by elevated intracranial pressure (ICP) with no identifiable underlying cause.

• The condition predominantly affects women aged 20 to 40 years and is strongly associated with obesity.

• Most patients present with a disabling headache that has a risk for permanent vision loss in up to 25% of cases.

< Diagnosis >

• Diagnosis of IIH requires a combination of clinical and imaging criteria, including a combination of papilledema, normal neurologic examination findings (except sixth nerve abnormality), neuroimaging features, normal cerebrospinal fluid (CSF) composition, and elevated opening pressure (≥250 mm).

• A number of neuroimaging features are described, including empty sella, flattening of the posterior aspect of the globe, distention of the perioptic subarachnoid space, and transverse sinus stenosis.

  
  

< Etiology >

• The cause of IIH remains unclear but is thought to be related to disordered CSF regulation, with potential CSF hypersecretion and/or reduced drainage.

< Management >

• There are a number of management strategies that have been adopted for the management of IIH, including weight loss, pharmacotherapy, lumbar puncture, optic nerve sheath fenestration, CSF shunting, and transverse sinus stenting.

< Case > 30/F, progressive vision changes

• Imaging findings before procedure

Empty sella

Distention of perioptic subarachnoid space

Bilateral transverse sinus stenosis

• Lumbar puncture procedure

Opening pressure: 300 mm CSF

20 mL of CSF withdrawn

Normal CSF analysis and culture results

• Post-puncture imaging

Post-puncture MRI showed reversal of imaging findings (Figure 1).

Reduction in optic nerve sheath diameter quantified for the first time.

Figure 1.  Magnetic Resonance Imaging (MRI) Performed at Day 4 After Lumbar Puncture (LP)

A, On the axial T1 postgadolinium image, the normal-appearing optic nerve sheath, sella turcica, and transverse sinuses are visualized. B, On the coronal T1 postgadolinium image, the diameter of the optic nerve sheath is better appreciated with the current diameter (4.4 mm, black circle) and the pre-LP diameter (6.9 mm, dashed white circle) is provided for comparison.

Figure 2.  Magnetic Resonance Imaging (MRI) Performed at 3 Months After Lumbar Puncture (LP)

A, On the axial T1 postgadolinium image, the optic nerve sheaths are dilated, the sella turcica is partially empty in appearance, and the transverse sinuses are reduced in caliber. B, On coronal T1 postgadolinium image, the diameter of the optic nerve sheath (5.3 mm, black circle) has increased compared with immediate post-LP caliber.

< Summary >

• The typical imaging findings of IIH are all markers of elevated ICP, which we believe are secondary to rather than the primary drivers of the condition.

• This notion is supported by the reversibility of all findings with CSF drainage. Of particular importance is the reversal of the transverse sinus stenosis, which is the target for transverse sinus stenting for IIH.

• The complete reversal of transverse sinus stenosis after the lumbar puncture suggests that the stenosis was secondary to elevated ICP.

• In patients with similar pathophysiology, transverse sinus stenosis may subsequently increase venous pressure, resulting in further impairment of CSF egress and increased ICP, and a vicious cycle ensues.

• However, the pathophysiologic underpinning the IIH phenotype is likely heterogeneous with other mechanisms, such as primary venous sinus stenosis, also presenting with a similar clinical syndrome.

• In the current case, we suspect impairment of CSF egress is the primary contributor to the clinical phenotype and responds to CSF drainage.

• Such pathophysiologic insights will ultimately be required to guide management in individual cases.

< 요약 >

• IIH의 전형적인 영상 소견은 모두 두개내 압력(ICP) 상승의 지표이며 이는  ICP 상승의 결과로 생각된다.

• 이러한 관점은 CSF 배출을 통해 모든 소견이 회복된다는 사실에 의해 뒷받침된다.

• 특히, 경정맥 협착의 회복은 IIH에 대한 경정맥 스텐트 시술의 주요 목표이다.

• 척수강천자(lumbar puncture) 후 경정맥 협착이 완전히 회복된 것은 이 협착이 ICP 상승의 결과였음을 시사한다.

• 유사한 병태생리를 가진 환자에서 경정맥 협착이 정맥압을 증가시킬 수 있으며, 이는 다시 CSF 배출을 방해하고 ICP를 더욱 증가시켜 악순환이 발생한다.

• 그러나 IIH의 병태생리학적 기초는 이질적일 가능성이 있으며, 일부 환자에서는 주 정맥 협착과 같은 다른 기전이 유사한 임상 증상을 나타낼 수 있다.

• 이 케이스에서는 CSF 배출 장애가 임상 증상의 주요 원인으로 추정되며, 이는 CSF 배출을 통해 개선된다.

• 이러한 IIH의 병태생리에 대한 통찰은 궁극적으로 개별 환자에 대한 관리 방향을 결정하는 데 필요할 것으로 생각된다.