Spontaneous intracranial hypotension: two steroid-responsive cases.

PURPOSE: Spontaneous intracranial hypotension (SIH) is characterised by orthostatic headache, low cerebrospinal fluid pressure and diffuse pachymeningeal enhancement after intravenous gadolinium contrast administration. Magnetic resonance imaging (MRI) often plays a crucial role for correct diagnosis. CASE DESCRIPTION: We described two similar cases of SIH, whose clinical and imaging features are typical for this pathology. At MRI brain scan, both patients showed diffuse and intense pachymeningeal enhancement and moderate venous distension and epidural vein engorgement. The two patients were treated with bed rest and oral steroid therapy, with complete and long-lasting symptomatic relief.
CONCLUSIONS: Orthostatic nature of headache is the most indicative clinical feature suggesting SIH; contrast-enhanced MRI provides definite imaging diagnostic findings. Conservative treatment coupled to steroid therapy is often sufficient to obtain complete disappearance of symptoms.

Introduction

Considered to be a benign condition, spontaneous intracranial hypotension (SIH) is defined as an idiopathic primary cerebrospinal fluid (CSF) pressure < 60 cm H2O in patients with no history of penetrating trauma or dural punction. It must be distinguished from secondary intracranial hypotension, iatrogenic or traumatic, the incidence of which is significantly larger [1-4].

Patients generally have variable orthostatic symptoms such as postural headache, neck pain, vertigo, anorexia, weakness, nausea or vomiting, and aspecific visual and hearing disturbances; sometimes radicular symptoms involving the upper limb can be present. Complications are sporadic and generally secondary to subdural haematoma [5].

SIH is most commonly related to unapparent CSF leak along the neuraxis, whose exact site cannot be localised and primitive cause assessed. According to Monro-Kellie’s hypothesis, SIH should be due to an alternate balance in the proportion of blood, CSF, and brain tissue in the central nervous system (CNS) [6].

Symptomatology usually disappears completely with conservative treatment and bed rest [7]. When spontaneous regression is not obtained with these measures, fluid restoration can be attempted in order to increase CSF volume by using intravenous or oral hydration, carbon dioxide inhalation, and steroid therapy [8]. In case of failure, epidural infusion of saline, epidural injection of fibrin glue, and epidural blood patches are considered an effective although more invasive treatment [9]. As a last therapeutic chance, surgical strategies may be required only in the case of documented meningeal defects [10].

Common diagnostic features at magnetic resonance imaging (MRI) examination include pachymeningeal thickening and post-contrast enhancement, venous enlargement and engorgement (specially of intracranial dural sinuses and spinal peridural plexuses), intrasellar arachnoid diverticulum or pituitary enlargement, subdural fluid collections, and deep brain swelling [5,11-14].

Case description

Case 1

A 35-year-old woman presented to the emergency service with a headache that developed over a week and progressively grew in intensity until it became unbearable. The patient reported suffering from periodic attacks of transient headache, sometimes associated with nausea and/or dizziness, beginning within 30 minutes of standing without remarkable triggering events. No other comorbidity was reported; neither use of medicines or contraceptives nor alcohol or illicit drug intake was discovered in her medical history. Neurological examination, blood analysis, and computed tomography (CT) scan performed at the emergency service were normal. Due to the ineffectiveness of conventional therapies, a standard MRI brain and cervical spine examination before and after intravenous gadolinium administration was performed. MRI showed diffuse pachymeningeal enhancement with positive venous distention sign, and reduced mamillopontine distance (about 5 mm) and cerebellar tonsils ectopia (about 4 mm) [15]. No associated subdural effusion was highlighted; callosal and pontomesencephalic angles were normal. As an occasional finding, a single CNS capillary telangiectasia was observed in the right putamen (Figure 1). The patient was treated with bed rest and steroid therapy (oral treatment with prednisone, 50 mg/day, with a gradual withdrawal in 30 days) [16], with complete symptomatic relief in a few days. After two months, follow-up brain MRI showed almost complete resolution of the imaging pathological findings (Figure 2).

Figure 1

A) Normal axial un-enhanced computed tomography brain scan, showing as occasional finding a capillary telangiectasia in right putamen. B) Sagittal TSE-T2w magnetic resonance imaging (MRI) shows reduced mamillopontine distance and cerebellar tonsils ectopia, with normal callosal and pontomesencephalic angles; C) venous distention sign is positive (white arrow). D) Axial, E) coronal, and F) sagittal SE-T1w MRI after intravenous gadolinium administration shows diffuse pachymeningeal enhancement; right putaminal capillary telangiectasia is clearly visible

Figure 2

After 2 months, follow-up SE-T1w magnetic resonance imaging on the three orthogonal plans after intravenous gadolinium administration shows almost complete resolution of the pathological diffuse pachymeningeal enhancement

Case 2

A 66-year-old woman with personal history of orthostatic headache associated with dizziness and vertigo came to our attention to perform a contrast-enhanced brain and cervical spine MRI scan, because of the activity-impairing nature of her condition. She was under therapy for essential hypertension and dyslipidaemia. No other comorbidity was noticed at outpatient clinical anamnesis, and neurological examination was normal. A previous cerebellopontine and temporal bone CT scan (performed because of invalidating vertigo attacks) did not bring to light any anomaly. MRI examination showed diffuse and intense pachymeningeal enhancement, involving also spinal dura; neither cerebellar tonsils ectopia nor herniation was noticed (Figure 3). A moderate venous distension and epidural vein engorgement were present; callosal angle, mamillopontine distance and pontomesencephalic angle were normal, and subdural effusions were absent. The patient was treated with bed rest and steroid therapy (oral treatment with prednisone, 50 mg/day, with a gradual withdrawal in 30 days) [16], with a progressive and long-term clinical improvement. After three months, follow-up brain and spine MRI showed a persistent dural contrast-enhancement (Figure 4), but it was less pronounced compared to the previous MRI examination. After the above-mentioned conservative therapy, the patient reported long-lasting complete disappearance of the symptoms.

Figure 3

A) Cervical spine and B-D) brain SE-T1w magnetic resonance imaging after intravenous gadolinium administration shows diffuse and intense pachymeningeal enhancement, involving also spinal dura. E) Axial FE T2* shows moderate venous distension and epidural vein engorgement

Figure 4

A-C) After 3 months, follow-up SE-T1w magnetic resonance imaging on the three orthogonal plans after intravenous gadolinium administration shows a partial reduction of the diffuse pachymeningeal enhancement

Discussion

We reported two cases of SIH with typical orthostatic symptoms and prompt relief of pain when the patients lay in a supine position, but symptoms recurred immediately when sitting or standing. The clinical picture is globally suggestive, but the diagnosis must be confirmed by contrast-enhanced brain and spine MRI examination. The exact incidence of this pathology is probably under-estimated because the diagnosis can be easily missed, especially when no history of dural puncture or trauma has been reported [10,17-19].

Among various endocranial findings, homogeneous and smooth pachymeningeal enhancement is one of the most common signs at brain MRI scan. Other signs may include increased blood volume in dural and epidural veins, subdural effusion, brain swelling and variation in CSF volume with consequent reduction of callosal angle, mamillopontine distance, and pontomesencephalic angle. Moreover, MRI could be useful to identify complications and possible sites of leak [4,5,10,18-20].

Similarly, spinal MRI can show a wide range of abnormalities, more inconsistent than endocranial findings, such as post-contrast dural enhancement and dilation of dural and epidural veins. In addition, it can lead to the identification of the probable site of leak, displayed as an area of increased signal in paraspinal soft tissue near the nerve roots [14,21-24].

When abnormal features are present, it is important to perform the differential diagnosis from conditions such as infections, vascular lesions, neoplasm, and immune-mediated disorders, distinguish axial from extra-axial enhancement pertinence and from disorders with spinal involvement [25-30].

As soon as the correct diagnosis is performed, an appropriate treatment can be put into practice. The most conservative therapeutic approach with bed rest and steroid administration should always be chosen in the first instance. If ineffective, epidural infusion of saline, epidural injection of fibrin glue, and epidural blood patches are considered as second options. Surgical strategies are generally required in the case of unsuccessful evolution, when clear meningeal defects have been documented. Complete resolution of symptoms after therapy is the final touchstone for the clinician [8-10,13,16].

Conclusions

In conclusion, we described two similar and relatively common cases of SIH, whose clinical and imaging features are typical of this pathology. Orthostatic nature of headache is the most indicative clinical element to suggest the hypothesis of SIH; contrast-enhanced MRI provides qualitative and quantitative findings, leading the radiologist and the clinician to the final correct diagnosis. Conservative treatment coupled to steroid therapy is often sufficient to obtain a complete disappearance of the symptoms.

Conflict of interest

The authors report no conflict of interest.