Case Report

A differential diagnosis in postural headache: herniation of a giant posterior fossa arachnoid cyst

Abstract

The causes of postural headache are usually associated with low intracranial pressure. However, there are still rare causes of posture-related headaches that are not associated with low intracraninal pressure and caused by pathologic processes. Herein, we report a patient with giant posterior fossa arachnoid cyst herniating below the level of foramen magnum presenting with postural headache, which has not been described previously in the literature. Emergency physicians should be aware that posterior fossa arachnoid cysts should be considered one of the differential diagnoses in patients with postural headache.

Postural headache was defined as one that occurs or worsens within 15 minutes after assuming the upright position and disappearing or improving within 30 minutes after resuming the recumbent position [1]. The causes of postural headache are usually associated with low intracra- nial pressure (ICP), including lumbar puncture, cerebrospi- nal fluid fistula, shunt overdrainage, or spontaneous intracranial hypotension. Other rare causes of posture- related headaches are not associated with low intracraninal pressure, including type I Chiari malformation, colloid cyst of the third ventricle, cerebellar hemorrhage, or postpartum postural headache due to superior sagittal sinus thrombosis [2-5]. Herein, we report a patient with giant posterior fossa arachnoid cyst herniating below the level of foramen magnum presenting with postural headache, which has not been described previously in the literature.

A previously healthy and headache-free 38-year-old man presented to the emergency department (ED) with an acute episode of moderate nonexplosive occipital headache for 5days. Standing aggravated the pain within 5 minutes, and lying down relieved the pain within 15 minutes. He did not have nausea, vomiting, photophobia, phonophobia, Unsteady gait, limbs weakness, blurry vision, or sensory deficiency. Vital signs were a temperature of 36.18C (978F), pulse rate of 64 beats/min, respiratory rate of

18 breaths/min, and blood pressure of 114/60 mm Hg. Physical and Neurological examinations were unremarkable. There was no history of epidural or Spinal anesthesia, previous attempt at lumbar puncture or trauma. His complete

blood count, biochemical profiles, and coagulation function were all normal. The low ICP headache was initially suspected, and he was suggested to follow up at the neurology clinic. Before discharge, the pain became more intense and caused vertigo after standing, which made him nearly disabled. A noncontrast computed tomography scan of the head was subsequently obtained, which revealed a giant posterior fossa cystic lesion. Magnetic resonance imaging with spin-echo sequences in axial and sagittal planes of the head revealed a giant infracerebellar arachnoid cyst herniat- ing below the level of the foramen magnum (Fig. 1). Dilatation of the aqueduct as well as the lateral and third ventricles was also found. A neurosurgeon was consulted, and cystoperitoneal shunt was performed. The patient showed marked improvement in his symptoms and had an uneventful recovery.

Headache represents up to 4% of all ED visits [6]. The primary task of the emergency physicians is to determine whether the patients have an organic, potentially life- threatening cause of headache. How to early appropriately select patients for emergency investigation and treatment of suspected critical secondary headache causes such as subarachnoid hemorrhage, meningitis, brain tumor with raised ICP is important. History and physical examination are emphasized in the guidelines published by The American College of Emergency Physicians and those of other groups [7]. Red flag features for headache with a serious cause include sudden onset of headache, onset of headache after

50 years of age, increased frequency or severity of headache, new onset of headache with an underlying medical condition, headache with concomitant systemic illness, focal neurologic signs or symptoms, papilledema, and headache subsequent to head trauma [8]. In the study by Sobri et al [9], the 20 red flag features adapted from Cleveland Clinic Headache Centre were used, and they suggested that patients with headache who have 3or more red flag features should have a prompt neuroImaging study. In contrast, patients with postural headache without special trauma history or neurologic deficiencies presenting to ED and impressing as low ICP headache are usually treated conservatively and are followed up at the neurological clinic. Most cases of low ICP headache resolved sponta- neously or responded well to bed rest and a generous intake of oral fluids. However, postural headache may also be caused by pathologic processes, such as cerebellar hemor- rhage or herniation of giant posterior fossa arachnoid cyst.

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Fig. 1 Magnetic resonance imaging of head showing a giant infracerebellar arachnoid cyst herniating below the level of the foramen magnum.

Hence, the value of early image study in ED must be considered while emergency physicians face a patient with posture headache to prevent delayed or missed diagnosis.

Posterior fossa arachnoid cysts are rare lesions that are considered to be mostly congenital in origin. The most common presenting symptoms are asymptomatically cyst, if symptomatically, gait disturbances and headache are the role complaints [10]. It may also produce symptoms typical of a tumor such as headache, dizziness, tinnitus, progressive sensorineural hearing loss, benign essential tremor, facial nerve palsy, and isolated twelfth nerve paresis [11-14]. The diagnosis was established on head computed tomography scan or magnetic resonance imag- ing. Themanagement of posterior fossa arachnoid cysts is somewhat controversial. Surgery is the standard treatment. Others prefer complete excision or fenestration of the cyst, but most prefer shunting procedures.

How the posterior fossa lesions caused postural headache in our patient is unclear. However, the hydro- cephalus and increased ICP suggest a mechanism other than low ICP. Valvular impaction due to herniation of the arachnoid cyst inthe foramen magnum may play a role. Williams [15] presented a patient with acro-osteolysis whose headache was developed through such a mecha- nism. An organic lesion and accompanying perifocal edema in the posterior fossa may block the outlets of the fourth ventricle. The hydrocephalus is likely to make further impaction, and the latter worsens the former in turn. When the patient assumed an upright position, the impaction excited the pain-sensitive intracranial tissues and

thereby provoked or worsened the headache. Lying down reduced the impaction to some degree and thus improved the severity of the headache.

In conclusion, emergency physicians should be aware that posterior fossa arachnoid cysts should be considered one of the differential diagnoses in patients with postural headache. Early image study must be considered while facing a patient with postural headache to prevent delayed or missed diagnosis.

Kuan-Che Lu MD

Division of Emeregncy Medicine

Keelung Hospital Keelung 202, Taiwan ROC

Chun-Chieh Chao MD

Department of Emergency Medicine

Taipei City Hospital Taipei 103, Taiwan ROC

Tzong-Luen Wang MD, PhD Chee-Fah Chong MD, MS Chien-Chih Chen MD, MS Emergency Department

Shin-Kong Wu Ho-Su Memorial Hospital

Taipei 111, Taiwan ROC School of Medicine

Fu Jen Catholic University Taipei 242, Taiwan

E-mail address: [email protected]

doi:10.1016/j.ajem.2007.04.005

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