Introducing the "Temporal Thumb Sign" in Pediatric Patients With New-Onset Idiopathic Seizures With and Without Elevated Cerebrospinal Fluid Opening Pressure

Incidence of temporal thumb sign in adult patients with idiopathic seizures with and without elevated opening cerebrospinal fluid pressure

OBJECTIVES

The temporal thumb sign (TTS) has emerged as a potential distinct magnetic resonance imaging (MRI) finding in pediatric patients with new-onset idiopathic seizures which is characterized by the protrusion of the inferior temporal gyrus into the skull base. This study investigated the prevalence and clinical implications of TTS in adult patients with idiopathic seizures, with or without elevated opening cerebrospinal fluid (CSF) pressure, and those diagnosed with idiopathic intracranial hypertension (IIH) without seizures.

MATERIALS AND METHODS

A retrospective study was conducted on 157 adults aged 18-40-years-old, divided into four distinct groups. Group 1 consisted of 52 patients diagnosed with idiopathic intracranial hypertension (IIH) without seizures. Group 2 included 27 patients with seizures and elevated opening CSF pressure. Group 3 comprised 39 patients with seizures but normal opening CSF pressure. Group 4 consisted of 39 controls. MRI or CT scans and lumbar puncture data were analyzed to evaluate the presence of TTS. Statistical analysis was performed to assess the prevalence, sensitivity, and specificity of TTS across groups. Significant differences were defined as p < 0.05.

RESULTS

Significant differences in TTS prevalence were observed between all groups (p < 0.001). TTS was most frequently detected in patients with seizures and elevated opening pressure (92.6%), followed by IIH patients without seizures (63.5%), and patients with seizures and normal opening pressure (61.5%). The control group exhibited a lower frequency of TTS (12.8%). Logistic regression demonstrated the association of TTS with seizure and elevated intracranial pressure (p < 0.001). Inter-rater reliability analysis showed excellent agreement between observers.

CONCLUSIONS

The results of this study suggest that the Kamali "Temporal Thumb Sign" is a novel neuroimaging feature associated with seizures and elevated opening CSF pressure in adult patients. High sensitivity (92.6%) of the TTS may yield it as a screening imaging marker in either brain CT or MRI scans in the emergency department, which could aid in suspecting possible elevated opening CSF pressure and proceeding with further workup. The association of TTS with seizures suggests a potential link between elevated intracranial pressure and structural alterations in the skull base with seizure presentation. The TTS may represent a distinct manifestation of intracranial hypertension, similar to temporal lobe encephaloceles.

KEY POINTS

Question This study investigates the prevalence and clinical implications of TTS in adults with idiopathic seizures at a single institution. Findings TTS was detected in 92.6% of patients with seizures and elevated CSF pressure. Clinical relevance TTS may serve as a sensitive marker for identifying elevated intracranial pressure in patients presenting with seizures to the emergency department.

Magnetic resonance signs of intracranial hypertension in children: a retrospective case-control study

The diagnostic accuracy of magnetic resonance (MRI) signs of intracranial hypertension (ICH) in children remains unclear. This study aims to assess how brain MRI signs of ICH correlate with cerebrospinal fluid opening pressure (CSFOP). A retrospective case-control study was conducted with 77 children aged 1 to 18 years, who underwent brain MRI and lumbar puncture with CSFOP measurement. A blinded radiologist evaluated key ICH signs, including distension of the perioptic subarachnoid space, optic nerve (ON) tortuosity, posterior scleral flattening, intraocular protrusion, and enhancement of the prelaminar ON, among others. Odds ratios, likelihood ratios, predictive values, sensitivity, specificity, and the area under the ROC curve (AUROC), were calculated in relation to CSFOP, adjusted for age and sex. The ICH group included 38 patients (49.3%) and the control group 39 (50.7%). The presence of four or more MRI signs of ICH provided the best diagnostic performance (specificity 92%, sensitivity 40%, AUROC 0.759) for identifying elevated CSFOP, particularly with intraocular protrusion of the prelaminar ON (p = 0.006, median CSFOP 49.6 cm H2O, p < .001) and papilledema (p = 0.042).

CONCLUSION

The presence of four or more MRI signs is associated with elevated CSFOP in children with non-structural ICH.

WHAT IS KNOWN

• The diagnostic accuracy of magnetic resonance imaging (MRI) signs of intracranial hypertension (ICH) in children remains unclear. • In children, there is no consensus about the most appropriate diagnostic criteria or robust evidence regarding the diagnostic performance of imaging signs for ICH.

WHAT IS NEW

• The presence of four or more MRI signs is associated with elevated cerebrospinal fluid opening pressure (CSFOP) in children with non-structural ICH. • Intraocular protrusion of the prelaminar ON, and papilledema are particularly relevant signs for identifying elevated CSFOP.

Seizures as the Initial Manifestation of Idiopathic Intracranial Hypertension Spectrum Disorder

Idiopathic intracranial hypertension (IIH) is a syndrome of isolated elevated intracranial pressure of unknown aetiology. The IIH spectrum has evolved over the past decade making the diagnosis and management more challenging. The neurological examination in IIH is typically normal except for papilloedema and possible cranial nerve 6 palsy. Recent publications have highlighted skull base thinning and remodelling in patients with chronic IIH. Resulting skull base defects can cause meningo-encephalocoeles, which are potential epileptogenic foci. We describe the clinical and radiological characteristics of five IIH patients with seizures and meningo-encephalocoeles as the presenting manifestations of IIH spectrum disorder.