Table 3.

Cognitive studies in adult population diagnosed with CM-I

Author	n	Control group	Age	Gender	Surgical treatment	Clinical signs and symptoms	Neuropsychological tests	Cognitive deficits	Neuroimaging findings
Pearce et al. (2006)	1	–	28	1 female	Yes *VSB	Ectopia: non-specified Scoliosis, hydrocephalus, quadriparesis	MMSE Others unspecified	Orientation; attention	N/A
Kumar et al. (2011)	10	10 Matched: age; gender	18–36	3 female 7 male	Non-specified	Ectopia: ≥ 5 mm Headache, dizziness	WAIS: Picture completion, Digit-symbol coding, Picture arrangement, Object assembly, Block design TMT	EF; visuospatial abilities; processing speed	MRI: • Ectopia below the foramen magnum DTI: • Decreased FA and increased MD in putamen, genu, splenium and fornix • Increased MD in cingulum • Increased AD in putamen, thalamus and fornix • Increased RD in fornix and cingulum
Del Casale et al. (2012)	1	–	18	1 male	No	Ectopia: non-specified Vertebral synostosis, basilar impression, modest dilatation of the central canal	RPM Stroop Corsi blocks Verbal fluency (phonological and semantic)	Visuospatial memory; psychomotor retardation; verbal fluency	MRI: • Ectopia below the foramen magnum • Posterior fossa volume and skull base anomalies
Mahgoub et al. (2012)	1	–	53	1 female	Non-specified	Ectopia: non-specified Impaired coordination, vertigo	MMSE MoCA Clock drawing DRS	EF; orientation; recall; attention; abstraction Generalized deficit	MRI: • Arnold-Chiari I malformation
Allen et al. (2014)	24	24 Matched: age; years of education	15–59	22 female 2 male	Yes (n = 24) *PFD	Ectopia: non-specified Headache, dizziness, balance issues	RAVLT Stroop Ospan Digity-symbol coding	Response inhibition; generalized slowing	MRI: • Cerebellar herniation below the foramen magnum
Klein et al. (2014)	2	–	a) 19 b) 38	2 male	No	a) Ectopia: 10 mm Headache, vertigo, syncope, muscle spasm b) Ectopia: 6 mm Headaches, muscle spasm	Stanford-Binet 5 RBANS CVLT CPT-II TMT WCST D-KEFS: Torre (only b) DSMB Grooved Pegboard ROCFT TPT WRAT	No significant deficits	MRI: • Cerebellar tonsils herniation below the foramen magnum • Posterior fossa volume anomalies
Allen et al. (2018)	638	102 Not matched	18–64	Non-specified	Mixed Yes (n = 341) *PFD	Ectopia: • PFD: 9.53 mm • Non-PFD: 7.01 mm Chronic pain	RAVLT	Immediate recall; attention	MRI: PFD (n = 121) and Non-PFD (n = 132) • Cerebellar tonsils herniation below the foramen magnum (> 5 mm)
Houston et al. (2018)	19	19 Matched: age; gender; years of education	35.4 ± 11.7	18 female 1 male	Mixed Yes (n = 2) *PFD	Ectopia: non-specified	RBANS: Digit-symbol coding, Digit forward Facial emotion perception task (NimStim database)	Emotional regulation; attention; processing speed	EEG and Event-Related potentials: Neurophysiological activity anomalies (consistent with a dysfunctional fronto-parietal attentional network)
García et al. (2018b)	39	39 Matched: age; gender; years of education	45.59 ± 11.9	32 female 7 male	No	Ectopia: 8.51 ± 4.81 Headache, dizziness, muscle pain, muscle weakness, trouble sleeping, syringomyelia (25.6%)	WAIS-IV: Digit backward Zoo map Stroop COWA SCVLT BNT ROCFT SDMT FEEL BFRT Happe’s Stories	EF; verbal fluency, visuospatial abilities, naming ability, verbal memory, processing speed, ToM	N/A
Besteiro and Torres (2018)	20	20 Matched: educational level	38–60	14 female 6 male	No	Ectopia: ≥ 5 mm	Stroop WCST CPT	EF; inhibition; attention	MRI: • Tonsillar herniation below the foramen magnum (> 5 mm)
Lázaro et al. (2018)	51	50 Matched: age; gender; educational level	48.62 ± 10.9	41 female 10 male	Mixed Yes (n = 27) *PFD	Ectopia: non-specified Syringomyelia (36.5%), hydrocephalus (4%)	COWA	Verbal fluency (phonetic and semantic)	N/A
García et al. (2018a)	76	76 Matched: age; gender; years of education	PFD: 51.32 ± 9.59 Non-PFD: 45.59 ± 11.9	63 female 13 male	Mixed Yes (n = 37) *PFD	Ectopia: PFD: 12.0 ± 7.0 Non-PFD: 8.51 ± 4.81 Headache, dizziness, neck-back pain, muscle pain, muscle weakness, trouble sleeping, subjective cognitive deficits, syringomyelia (40.5%PFD/25.6%Non-PFD), hydrocephalus (13.5%PFD)	WAIS-IV: Digit backward Zoo map Stroop COWA SCVLT BNT ROCFT SDMT FEEL Happe’s Stories	EF; verbal fluency; spatial cognition; naming ability; verbal memory; processing speed; emotional facial recognition; ToM	N/A
Lacy et al. (2019)	18	18 Matched: age; years of education	30 ± 8.62	15 female 3 male	No	Ectopia: non-specified	MMSE RBANS Stroop D-KEFS: Card sorting TMT-B	Generalized deficit; verbal fluency; immediate memory; spatial planning abilities	N/A
Houston et al. (2019)	18	18 Matched: age; gender; years of education	34.4 ± 12.7	17 female 1 male	No	Ectopia 12.4 ± 4.9 mm Headache, neck pain, limb pain, fatigue, dizziness, tinnitus, insomnia, difficulty concentrating, forgetfulness, syringomyelia (22.2%)	RBANS	Attention, immediate and delayed memory	MRI: • Cerebellar tonsils herniation below the foramen magnum. Greater descent correlated with worse delayed memory • Posterior fossa volume anomalies and shorter intracranial heights. Greater osseous areas correlated with better attention
García et al. (2020b)	26	26 Matched: age; gender; years of education	47.15 ± 14.6	22 female 4 male	Mixed Yes (n = 8) *PFD	Ectopia: 7.74 ± 3.95 Headache, body pain, muscle weakness, sensory disturbances, dizziness, vertigo, instability, fatigue, visual and hearing alterations, nystagmus, swallowing problems, sphincter problems, sleeping disturbances, cognitive subjective deficits, syringomyelia (26.9%), hydrocephalus (7.7%)	WAIS-IV: Block design, Visual puzzles ROCFT JoLO WAT	Visuospatial abilities (mental imagery)	N/A
García et al. (2020a)	26	26 Matched: age; gender; years of education	47.15 ± 14.6	22 female 4 male	Mixed Yes (n = 8) *PFD	Ectopia: 7.74 ± 3.95 Headache, body pain, muscle weakness, sensory disturbances, dizziness, vertigo, instability, fatigue, visual and hearing alterations, nystagmus, swallowing problems, sphincter problems, sleeping disturbances, cognitive subjective deficits, syringomyelia (26.9%), hydrocephalus (7.7%)	Faux Pas test Happé’s Stories Ice-cream Van task FEEL WAT	ToM	N/A
Almotairi et al. (2020)	13	–	37 ± 12	10 female 3 male	Yes (n = 13) *PFD	Ectopia: 5–12 mm (46%) 12.1–20 mm (38%)  > 20 mm (15%) Headache, weakness, sensory loss, blurred vision, swallowing difficulty, tremor, gait difficulty dysarthria, nausea, syringomyelia (54%)	n = 11 (2 missed) WAIS: Digit-symbol coding RAVLT Stroop BVMT-R Grooved Pegboard	No significant deficits *Improvement after surgery: verbal learning, psychomotor and verbal speed, inhibition	N/A
Houston et al. (2020)	18	18 Matched: age; gender; years of education	33.8 ± 11.4	18 female	Mixed Yes (n = 2) *PFD	Ectopia 12.5 ± 4.6 mm Headache, neck pain, limb pain, fatigue, dizziness, tinnitus, insomnia, difficulty concentrating, forgetfulness, syringomyelia (22.2%)	RBANS: Digit-symbol coding, Digit forward	Attention; processing speed	DTI: • Increased FA in internal capsule, corpus callosum, stratum, longitudinal fasciculus, middle cerebellar peduncle and corona radiata • Decreased RD in the left anterior corona radiata • Decreased MD in the corpus callosum and left superior longitudinal fasciculus *After pain effect controlling, FA, RD and MD differences were eliminated
Houston et al. (2021)	17	18 Matched: age; years of education	32.5 ± 10.1	16 female 1 male	Mixed Yes (n = 2) *PFD	Ectopia 12.6 ± 4.8 mm Headache, neck pain, limb pain, fatigue, dizziness, tinnitus, insomnia, difficulty concentrating, forgetfulness, syringomyelia (22.2%)	RBANS: Digit-symbol coding, Digit forward	Attention	fMRI: • Hyperconnectivity between the PCC and the left globus pallidus, and between the cerebellar lobule VIII and the left postcentral gyrus and vermis IX and the precuneus • Hypoconnectivity between PCP and the right supramarginal gyrus
Seaman et al. (2021)	Pre: 26 Post: 19	–	Pre/post: 18.4–56.2	Pre: 23 female 3 male Post: 19 female	Yes (n = 26) *PFD (extradural or intradural)	Ectopia 15.2 ± 4.8 mm Headache, bulbar signs or symptoms, nystagmus, scoliosis, syringomyelia (42%)	WAIS-IV: Similarities, Vocabulary, Block design, Matrix reasoning, Digit span, Symbol search, Digit symbol coding Stroop RAVLT TMT (A-B) COWA WRAT ROCFT WMS: Spatial span JoLO Grooved Pegboard	Visuospatial abilities; visual memory; psychomotor abilities *No differences were found after surgery	N/A
Yilmaz et al. (2022)	29	33 Matched: age; gender educational level	37.6 ± 9.9	24 female 5 male	No	Ectopia: non-specified	MMSE Stroop Kent EGY Porteus Maze NSLT	Generalized cognitive deficit and slowing; EF; response inhibition	N/A

Sociodemographic, clinical, cognitive, and imaging data are reported from CM-I patients, not control groups

AD Axial Diffusivity, BFRT Benton Facial Recognition Test, BNT Boston Naming Test, BVMT-R Brief Visuospatial Memory Test-revised, CPT Conners` Continuous Performance Test, CVLT California Verbal Learning Test, D-KEFS Delis-Kaplan Executive Function System, DRS Dementia Rating Scale, DSMB Dean–Woodcock Sensory Motor Battery, EF Executive Functioning, FA Fractional Anisotropy, FEEL Facially Expressed Emotion Labeling Test, JoLO Judgment of Line Orientation Test, MD Mean Diffusivity, MMSE Minimental State Examination, MoCA Montreal Cognitive Assessment, NSLT Number Sequencing Learning Test, Ospan Operation Span Task, PFD Posterior Fossa Decompression, PCC Posterior Cingulate Cortex PCP Posterior Cerebellar Pathway, RAVLT Rey Auditory Verbal Learning Test, RD Radial Diffusivity, RBANS Repeatable Battery for the Assessment of Neuropsychological Status, ROCF Rey-Osterrieth Complex Figure Test, RPM Raven’s Progressive Matrices, SDMT Symbol Digit Modalities Test, SPVLT Spain-Complutense Verbal Learning Test: TMT Trail Making Test, ToM Theory of Mind, TPT Tactile Performance Test, VSB Ventriculoperitoneal Shunt Blockade, WAIS Wechsler Adult Intelligence Scale, WAT Word Accentuation Test, WCST Wisconsin Card Sorting Test, WMS Wechsler Memory Scale, WRAT Wechsler Reading Ability Test