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Neurologic manifestations in children with COVID-19 from a tertiary center in Turkey and literature review

Background Since December 2019, coronavirus disease 2019 (COVID-19) has become a global pandemic caused by highly transmissible severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although respiratory disease and multisystem inflammatory syndrome in children (MIS-C) are main clinical presentations in children, numerous neurological manifestations are being described increasingly. We aimed to investigate new onset neurological symptoms associated with SARS-CoV-2 in pediatric patients in order to establish a possible relationship as well as to understand the underlying pathophysiological mechanisms between SARS-CoV-2 infection and neurological findings. Methods We analyzed retrospectively children who had neurologic manifestations temporally associated with SARS-CoV-2 infection at Hacettepe University İhsan Doğramaci Children's Hospital. We performed a literature search between March 20, 2020 and March 30, 2021. Articles that report children with COVID-19 related neurological manifestations were included. Results We have observed 15 consecutive cases with new onset neurological manifestations along with confirmed SARS-CoV-2 infection. Age at hospitalization ranged from three months to 17 years. Ten patients had central nervous system involvement, and most common manifestation was encephalopathy (5/10), which is also one of the most common manifestations of the patients mentioned in the relevant 39 articles we reviewed. Conclusion Children with COVID-19 can present with neurologic findings such as encephalopathy, seizures, cerebrovascular events as well as abnormal eye movements. Clinical suspicion and awareness are required to show the association between neurologic manifestations and COVID-19.


Introduction
Since December 2019, the coronavirus disease 2019 (COVID- 19), caused by the highly transmissible severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global pandemic [1]. The disease remains a challenge to clinicians due to its different manifestations. Numerous neurological complications have been described in patients with SARS-CoV-2 infection. These include both the central and peripheral nervous system, range from mild to severe, and can occur in patients with severe to asymptomatic COVID-19 due to different pathophysiological mechanisms [1][2][3][4][5][6].
Since neurological complications have long been identified in

Outcome measures
The results were divided into central and peripheral nervous system manifestations. The literature review aimed to reveal the possible link between SARS-CoV-2 infection and neurological complications.

Patients
During the study period, a total of 312 children with COVID-19related illness were hospitalized. Their median age was 10.8 years (range: 1 month-17.5 years). Fifteen (4.8%) consecutive cases had acute new-onset neurological manifestations associated with SARS-CoV-2 infection. The age of these patients at admission ranged from 3 months to 17 years, with a median age of 5 years. The female-male ratio was 6 (40%) to 9 (60%). Three patients had underlying disease: one with asthma, one with factor V Leiden mutation, and one with sensorineural hearing loss. The clinical presentations and outcomes of patients are given in Table 1.
Six patients were classified as para-infectious: four were PCR positive, and two tested negative but had more than one SARS-CoV-2 PCR positive close household contact. Both PCR negative para-infectious patients tested seropositive for SARS-CoV-2 IgG on the 18th day after their initial symptoms. Nine postinfectious patients tested PCR negative for SARS-CoV-2, but all were SARS-CoV-2 IgG positive at admission. All had a history of contact with at least one SARS-CoV-2 PCR positive close household contact three to six weeks before admission. One patient was PCR positive three weeks before admission while two had symptoms of upper respiratory infections at the time of contact. Six of the nine patients classified as postinfectious diagnosed with MIS-C.

Isolated central nervous system involvement
Of the 15 patients with neurological manifestations, 10 (66.6%) had CNS involvement, most commonly encephalopathy. Five of 10 patients (50%) with CNS involvement presented with encephalopathy, and two adolescents had hallucinations and delirium; all had diagnoses of MIS-C, and one developed posterior reversible encephalopathy syndrome (PRES) during follow-up. The second most common CNS manifestation was seizure (4/10; 40%): two patients were admitted with febrile seizure, one with febrile status epilepticus, and the other with afebrile status epilepticus. Three of the patients with seizures were in the parainfectious group. One patient with abnormal eye movements had tonic eye deviation in upward and lateral gaze followed by faster compensatory downward eye movement, with no associated nystagmus or abnormal head or extremity movements. On her magnetic resonance imaging (MRI), punctate diffusion restriction in the dorsal medulla oblongata was detected suggestive of brainstem involvement.
Another patient presented with diplopia, papilledema, and sixth cranial nerve palsy due to increased intracranial pressure (ICP). A 3year-old boy with a 1-year history of previous stroke associated with factor V Leiden mutation, maintained on acetylsalicylic acid (ASA) prophylaxis, presented with left localized numbness. He was eventually diagnosed with acute tri-ventricular hydrocephalus due to cerebral aqueduct obstruction.

Isolated peripheral nervous system involvement
Two patients (13.3%) had myositis and elevated creatine kinase (CK) levels during the acute phase of COVID-19. Both were treated with intravenous alkaline hydration, and one (Case 2) experienced rhabdomyolysis.
One patient (6.6%) with MIS-C had tingling and pain in both hands and feet on the 15th day of admission. On neurological examination, he had no motor deficits. Electromyography (EMG) was performed on the day of emerged symptoms. The pain was suspected to be neuropathic and he was started on gabapentin treatment. Although his EMG was reported as normal, his symptoms resolved completely under gabapentin treatment.

Both central and peripheral nervous system involvement
Two (13.3%) MIS-C patients had both central and peripheral nervous system involvement, presenting with encephalopathy and developing critical illness neuromyopathy on the 7th and 26th days of admission, respectively.

Cerebrospinal fluid examination
Nine (60%) patients had lumbar punctures; only three cerebrospinal fluids (CSF) were analyzed for SARS-CoV-2 PCR and SARS-CoV-2 IgG, with negative results (Table 1). Two patients had high CSF protein levels attributed to lumbar puncture procedures being traumatic hence crosscontamination of CSF. Red blood cells were observed on direct microscopic examination. The remaining patients' CSF samples direct microscopic examination did not reveal any cells.
A viral panel including herpes simplex virus (HSV) types 1 and 2,  Cerebrospinal fluid cytocentrifuge and cytopathologic examination were performed for two patients diagnosed with ICP to exclude neoplastic causes. The examination results revealed activated macrophages.

Neurophysiological studies
The neurophysiological findings of the cases are summarized in Table 2. A total of six patients had electroencephalogram (EEG) study, four patients, diagnosed with seizure, had EEGs recorded at admission, all but one had normal EEGs. Electrographic seizure activity on right parieto-occipital region and low voltage background detected in one patient, diagnosed as febrile status, at admission and on the 3rd day of hospitalization.
EMG was performed in three patients; all were hospitalized with the diagnosis of MIS-C. One patient experienced extremity pain without motor deficit on the 15th day, and EMG obtained the same day was normal.
Case 11 had diffuse weakness on the 7th day of admission. She could move her limbs only when gravity was eliminated, and her EMG revealed myopathic changes.
Case 12 experienced more pronounced weakness in the lower extremities, noted just after extubation on the 26th day. He could move his legs against gravity and was capable of minimal resistance in his arms. He was diagnosed with motor axonal polyneuropathy on EMG performed 2 months after discharge.

Neuroimaging Studies
The neuroimaging findings in all cases are summarized in Table 2. Eleven patients underwent neuroimaging. Three had only cranial

Outcomes
All the patients were re-evaluated on the 15th day and at the first, second, third, and sixth months after discharge. Outcomes were assessed at the final visit (median: 3 months, range: 1-6 months). Overall, 12 (80%) patients had no disability, assessed by the modified Rankin Scale (mRS = 0), and three (20%) had mild disability.
Four patients who had seizures experienced no seizures after discharge. Three were on antiseizure medication with levetiracetam. The abnormal eye movements detected in one patient resolved spontaneously. The papilledema and sixth nerve paralysis of the patient with secondary intracranial hypertension resolved in 3 months.
One patient with acute tri-ventricular hydrocephalus returned his baseline neurological status following surgery. Two patients with myositis and elevated CK had no neurological or renal impairment at hospital discharge or follow-up visits.
Of the six patients with MIS-C, three recovered completely. However, the remaining three were discharged with mild to moderate muscle strength loss and required assistance for walking.

Literature review
An increasing number of neurological complications in patients with COVID-19 continue to be reported worldwide. Common features of the 211 children with neurological manifestations in the literature we reviewed are summarized in Table 3. Yea et al. [15] reported 31 patients with only headache, so we excluded these and studied 180 children with specific neurological manifestations temporally associated with SARS-CoV-2 infection. We prepared a chart of the most common presenting neurological features in children with COVID-19, using a combination of our data and the literature review (Fig. 3). The ages ranged from 2 months to 17 years. Ninety-five (53.4%) patients were female. Children with MIS-C comprised half of the patients with neurologic manifestations (n = 90, 50.6%).

Central nervous system involvement
3.2.1.1. Cerebrovascular disease. Cerebrovascular diseases including ischemic and hemorrhagic strokes, venous thrombosis, cerebral arteriopathies, and vasculitis were the most common neurological manifestations related to SARS-CoV-2 infection. We reviewed 36 (20.22%) cases with cerebrovascular complications. Some were due to underlying diseases, and some had strokes during ECMO and life support. For example, LaRovere et al. [16] reported 12 cases with acute ischemic or hemorrhagic stroke, five of whom experienced cerebrovascular event during ECMO. Two cases had underlying vascular malformations (one with arteriovenous malformation and the other with Moya syndrome). In a study of neuroimaging manifestations in children, Lindan et al. [17] reported seven cases with thromboembolic or vasculitic stroke. In addition to ECMO treatment complications, acute cerebral artery infarctions and subarachnoid hemorrhages were reported [16]. Bastidas et al. [18] reported a 13-year-old girl with sinus vein thrombosis. She presented to the hospital with severe headache and impaired Table 2 Neuroimaging and neurophysiological study findings.
consciousness. On the fifth day of admission, a body angio-CT scan was performed; she had multiple vein thrombosis including superior sagittal sinus and pulmonary thromboembolism and bilateral deep femoral and iliac vein thrombosis.

Seizures, status epilepticus.
Seizures were reported in 28 (15.5%) patients. Four (2.2%) were febrile seizures and were the only presenting complaint of SARS-CoV-2 infection. All the seizure episodes were acutely symptomatic, and most appeared during the febrile period. A 14-year-old girl presented with fever, cough, and hypoxia. During hospitalization, she had episodes of seizures and apnea. Neurologic examination was normal. Cerebrospinal fluid examination was in normal ranges, and CSF culture was negative. She had epileptiform activity on EEG. Craniospinal MRI was normal. She was discharged with no apneic or seizure episodes after levetiracetam [19]. Afebrile seizures were also reported as the only presenting complaint. Garcia Howard et al. [20] and Bhatta et al. [21] reported two patients with afebrile seizures. Garcia Howard et al. [20] reported that a 3-month-old girl with respiratory symptoms had afebrile seizure episodes. She had a normal EEG pattern and brain MRI. Bhatta et al. reported an 11-year-old boy with two episodes of generalized tonic-clonic seizures. He had no history of fever or respiratory symptoms. Both were asymptomatic during follow-up.
Swarz et al. [22] reported that a 9-year-old boy with no medical history presented with focal SE. He was afebrile and had no meningeal irritation findings. Head CT was normal, and EEG showed continuous delta slowing throughout the right hemisphere without epileptiform activity. In a case series reported from Chile, one patient among 13 cases presented with SE [23].
3.2.1.3. Encephalopathy, encephalitis and encephalomyelitis. Of the 180 patients, 26 (14.4%) were reported to have encephalopathy or a low level of consciousness. Encephalopathy was reported in patients with MIS-C and acute COVID-19. Abdel-Mannan et al. [24] reported four cases of encephalopathy with MIS-C in the United Kingdom. Three had diffuse slow activity on EEG and signal changes in the splenium of the corpus callosum on MRI. LaRovere et al. [16] reported 15 cases with severe encephalopathy, and eight were diagnosed with MIS-C. Most patients recovered while their inflammatory response resolved.
Encephalitis associated with SARS-CoV-2 infection has been reported. Bhavshar et al. [25] reported a 16-year-old boy with somnolence for two days and generalized weakness. He could not ambulate without assistance. During the emergency department evaluation, he had seizures. CT was normal, and he had a lumbar puncture. CSF findings were compatible with encephalitis. Ahsan et al. [26] reported myelin oligodendrocyte glycoprotein antibody encephalitis (MOG) in a 7-year-old girl from the United States of America. Sánchez-Morales et al. [27] reported a 14-year-old boy with anti-NMDA-R encephalitis. He had altered behavior and mental status, seizures, insomnia, and orolingual dyskinesias. Anti-NMDA-R antibody was positive in the CFS sample. His seizures recovered, but psychiatric symptoms continued. Acute disseminated encephalomyelitis (ADEM) was reported in 9 (5%) cases. Lindan et al. [17], also reported 16 cases of neuroimaging compatible with an ADEM-like pattern, but this did not mean that patients met the clinical definition for ADEM. A 12-year-old girl presented with neurologic complaints such as acute, progressive, and bilateral motor deficit. She developed respiratory symptoms two days after the neurological complaints.

Peripheral nervous system involvement
3.2.2.1. Guillain-barre syndrome. Ten (5.5%) patients were reported with the diagnosis of GBS and eight (80%) were male. The patients were aged between 8 and 15 years. All had positive SARS-CoV-2 antibody results. Sandoval et al. [23] reported that an 8-year-old boy presented with a progressive ascendant acute flaccid tetraparesis, areflexia, and multiple cranial nerve palsies, with an EMG and nerve conduction study (NCS) compatible with the acute motor axonal neuropathy (AMAN) GBS variant. Frank et al. [28] also reported AMAN type GBS. Sánchez-Morales et al. [27] and Khalifa et al. [29] reported four cases of GBS with acute inflammatory demyelinating polyneuropathy (AIDP). All patients were discharged, and some needed physical rehabilitation for a period.

Myositis.
A previously healthy 10-year-old girl who presented with fever and myalgia was diagnosed with myositis and rhabdomyolysis [27]. She had a positive SARS-CoV-2 PCR result. She had acute myositis with respiratory symptoms.

Geographic location of cases with nervous system involvement due to SARS-CoV-2
The most common published cases with nervous system involvement were in the United States of America, followed by the United Kingdom, Chile, and Mexico (Supplementary Table 1).

Discussion
In the present study conducted in a tertiary center involving case series of hospitalized children and adolescents with COVID-19 and/or MIS-C, neurologic involvement incidence was 4.8%. Most of the patients (80%, n = 12) with neurologic findings were previously healthy and most of the neurological manifestations (n = 15) were transient and resolved at the time of hospital discharge. Three patients had mild to moderate new neurologic disabilities persisting at discharge.
In both adults and children, a wide range of neurological symptoms have been reported, ranging from relatively mild symptoms like fatigue, headache, and anosmia to more severe clinical presentations like encephalopathy, seizures, and stroke [2][3][4][5]. In these reports neurologic symptoms varied by age; while seizures and status epilepticus observed in young patients, headache, loss of taste and smell and fatigue were observed in older patients. Consistent with these findings, four patients with seizures (three with para-infectious febrile seizure and one with postinfectious afebrile SE) included in the study were young children. A 3-month-old girl had her first seizure during the postinfectious period and had punctate diffusion restriction in the posterior limb of the internal capsule on MRI. No other etiological factor than COVID-19 was diagnosed. The clinical outcome was good, and all these patients were seizure-free during three-to-six-month follow-up with monotherapy. They had no neurological sequelae (mRS:0). SARS-CoV-2 virus was initially thought unable to pass through the blood-brain barrier (BBB) or enter the nervous system. However, postmortem studies on the cerebral pathology of SARS-CoV-2 have identified that it could pass the BBB, and neuro-invasion could use olfactory nerve channels and trans-synaptic viral transfer [10,54]. Also possible is a "Trojan horse" mechanism of the virus using macrophages to enter the central nervous system [55]. Neural cells, astrocytes, microglia, and brain microvascular endothelial cells express ACE2, a SARS-CoV-2 spike (S) protein binding receptor [10,11]. Once inside the nervous system, the virus can infect those cells and cause neural damage or inflammation. This might help to explain the para-infectious events. Possible pathophysiological mechanisms of neurological involvement in our pediatric cases might be the direct viral invasion of neuronal structures through infecting olfactory system, or through types 2 and 3 innate immune cells. The role and distribution of ACE-2 receptors of over different areas of brain, especially brainstem should be considered in pathophysiology. Postinfectious inflammatory processes, dysregulated cytokine cascade, autoimmunity, and vascular events including thrombosis, infarction, or hemorrhages might be responsible for pathophysiology of neurological involvement [56][57][58].
Few studies have suggested the role of cytokines in febrile seizures [59,60]. Some have reported that proinflammatory cytokines such as interleukin-6 (IL-6), interleukin-8 (IL-8), and interferon-γ (IFN-γ) are increased in febrile seizures. We did not study the cytokine/chemokine profiles of our cases because of the retrospective nature of the study. Cytokines were reported to play a role in the pathophysiology of SARS-CoV-2 infection [61]. They may also be involved in the pathophysiology of COVID-19-related febrile or afebrile seizures. Important proinflammatory cytokines such as IL-6, TNF-α, IFN-γ, and IL-17 have been linked to the pathogenesis of SARS-CoV-2 infection [62,63]. They may play a key role in epileptic pathogenesis. They also lead to seizures by increasing glutamate and decreasing GABA in the cerebral cortex and hippocampus [62,64]. Therefore, we hypothesize that proinflammatory cytokines might have a crucial role in the pathogenesis of seizures due to SARS-CoV-2 both during the para-infectious and postinfectious periods.
We observed global cerebral involvement in five MIS-C patients with severe encephalopathy. All had changes in cognition: three had visual, auditory, or tactile hallucinations, and two were in a delirium state for two days. Two MIS-C patients had meningeal irritation at admission. Two MIS-C patients with severe and progressive disease course had vascular findings on MRI. MRI of one patient revealed infra-and supratentorial multiple microhemorrhages, suggestive of small-vessel vasculitis, bilateral middle cerebral artery (MCA) stenosis consistent with medium-vessel vasculitis and meningioependymal contrast enhancement. Computed tomography angiography imaging of the other patient showed stenosis in the upper truncus of the right MCA and paucity of the distal branches of the MCA. These neuroimaging findings suggested vascular endothelial cell damage, consistent with the cases in the literature review [16][17][18]27,36,37,45,46]. Postinfectious neurological manifestations of MIS-C cases, might be the result of immune-mediated responses. The exaggerated cytokine release leading to endothelial damage, the hallmark of MIS-C pathogenesis, might be responsible for the disruption of BBB [54,65].
Previous case reports in children stated the association between COVID-19 and secondary ICP [53]. Consistently, in our series, one patient with increased ICP was diagnosed with secondary ICP related with COVID-19. Another patient diagnosed with factor V Leiden homozygous mutation, maintained on ASA and had a stroke history had increased ICP. He was diagnosed with acute hydrocephalus due to a web formation in Aquaeductus Sylvius and underwent an endoscopic third ventriculostomy. During the course of COVID-19 he did not have a new-onset stroke and his MRI only revealed contrast enchantment. Therefore, we hypothesized that the web formed in the Aquaeductus Sylvius might have resulted from inflammation associated with COVID-19.
Five patients had peripheral nervous system impairment: one had neuropathic pain, two experienced primarily encephalopathy and developed critical illness neuromyopathy during the hospital stay, and two had myositis and elevated CK levels. Severe inflammation, several secondary effects of critical illness, medications and possibly direct effects of SARS-CoV-2 may be responsible for peripheric nervous system involvement [66][67][68]. A significant number of patients with severe COVID-19 hospitalizations may be prolonged and may require mechanical ventilation, anesthetic medications, hence they are at risk of developing acquired weaknesses such as critical illness polyneuropathy, myopathy, and polyneuromyopathy. All conditions have been reported in adults with COVID-19, and severe inflammation is suggested to increase the risk [67,68].
So far, few data are available to describe SARS-CoV-2 specific CSF findings. In the present study, nine patients had CSF analysis, four had seizures, two had encephalopathy during MIS-C, one had secondary ICP, one had abnormal eye movements, and one underwent ventriculostomy for hydrocephalus. Pleocytosis was not detected in any samples. SARS-CoV-2 PCR and antibody testing could be studied in three out of the nine CSF samples, and all three were negative. Overall, the results of CSF studies of our patients were consistent with non-infectious inflammation processes during the course of disease. Bellon et al. [69] evaluated CSF samples of 31 adults with positive RT-PCR for SARS-CoV-2 from respiratory specimens and with neurological findings. None were positive for SARS-CoV-2 RNA by RT-PCR. All patients tested positive for anti--SARS-CoV-2 IgG antibodies in the serum, and 78% had antibodies in the CSF. According to the findings of this report, SARS-CoV-2 was not detected in most CSF samples. However, the detection of antibodies could suggest the possibility of an immune mechanism rather than viral invasion, requiring further clarification. Cytopathological evaluation of CSF samples has shown increased numbers of lymphocytes and macrophages. High numbers of macrophages were reported in 60% of CSF specimens' cytological examination [70]. Two of our patients had cytopathological examination of CSF samples, and activated macrophages were prominent, in accordance with the literature. Increased macrophages could suggest microglial activation, known to induce expression of inflammatory responses such as cytokines, chemokines, and matrix metalloproteases [70,71]. These findings could provide a preference for anti-inflammatory or immunomodulatory treatment for neurological complications if supported by further studies.
We reviewed a broad range of severe neurological findings of pediatric patients, including central nervous system diseases (such as ADEM, severe encephalopathy with corpus callosum splenial lesions, seizures, ischemic strokes, cerebral venous sinus thrombosis, acute cerebral edema, and central nervous system infections) and peripheral nervous system diseases (such as GBS, myelitis, cranial neuropathies, and severe myositis) associated with SARS-CoV-2 infection. Neurologic involvement associated with SARS-CoV-2 possibly have multiple underlying mechanisms leading to para-or post-infectious events. The activation of cytokines and chemokines might be one of the key processes of postinfectious neurological involvement in MIS-C patients. In our case series severe encephalopathy observed in MIS-C patients resolved completely with anti-inflammatory treatment. Some recent studies have reported neuropilin-1 (NRP1) as a receptor for the SARS-CoV-2 spike protein [72]. Moutal et al. [73] reported that the SARS-CoV-2 spike protein interacts with NRP1 to induce signaling in nociceptors. This could be a mechanism for pain during or after SARS-CoV-2 infection; another hypothesis is high cytokine levels during severe COVID-19 or MIS-C [74]. These theories could support the peripheral nervous system involvement that we report in a patient with neuropathic pain during MIS-C and patients with critical illness neuromyopathies.
Our study has several limitations, this single-center retrospective observational study spans a short period. The full spectrum of the neurologic symptoms might have been underestimated in children, especially in young children. Neuroimaging could not be obtained for all patients. We could not have a continuous EEG monitoring, so we might have missed electrographic seizures. The follow-up period of patients is short. Nevertheless, we were able to demonstrate the outcomes of patients with a formal scale.

Conclusion
We presented pediatric patients with new onset neurologic manifestations associated with SARS-CoV-2 infection. Our data showed that children, especially infants may present with neurologic findings such as seizures or abnormal eye movements as only symptoms of COVID-19. With growing evidence of the role of immune response playing a key role on many neurologic para-infectious and postinfectious manifestations of COVID-19, it is plausible that children with unusual signs and symptoms should be tested for COVID-19. Pediatricians should be aware of such atypical presentations of COVID-19 infection for early diagnosis.