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ABPath Neuropathology study materials
ABPath Neuropathology study resources

ABPath Neuropathology practice questions

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Question 1Normal neuroanatomy

Which cell type produces the myelin sheath of axons in the central nervous system?

  1. Microglial cell
  2. Oligodendrocyte Correct answer.
  3. Astrocyte
  4. Schwann cell

Explanation

In the CNS, a single oligodendrocyte extends multiple processes, each wrapping a segment of an axon to form myelin. Schwann cells perform this role only in the peripheral nervous system.

Question 2Normal neuroanatomy

The CSF-containing space that lies between the arachnoid mater and the pia mater is called the:

  1. Subarachnoid space Correct answer.
  2. Subdural space
  3. Epidural space
  4. Virchow-Robin space

Explanation

Cerebrospinal fluid circulates in the subarachnoid space, which lies deep to the arachnoid mater and superficial to the pia mater. The epidural and subdural spaces are potential spaces that do not normally contain CSF.

Question 3Normal neuroanatomy

Which cranial nerve provides motor innervation to the muscles of mastication?

  1. Hypoglossal nerve
  2. Trigeminal nerve Correct answer.
  3. Glossopharyngeal nerve
  4. Facial nerve

Explanation

The mandibular division of the trigeminal nerve supplies the muscles of mastication, including the masseter, temporalis, and pterygoids. The facial nerve supplies muscles of facial expression instead.

Question 4Normal neuroanatomy

The layer of the cerebellar cortex that contains Purkinje cell bodies is the:

  1. Molecular layer
  2. White matter
  3. Granule cell layer
  4. Purkinje cell layer Correct answer.

Explanation

Purkinje cells form a single row of large somata in the Purkinje cell layer, between the molecular and granule cell layers. Their dendrites arborize in the molecular layer while their axons project into the white matter.

Question 5Normal neuroanatomy

Which structure forms the floor of the third ventricle?

  1. Hypothalamus Correct answer.
  2. Corpus callosum
  3. Fornix
  4. Thalamus

Explanation

The hypothalamus forms the floor and much of the lateral walls of the third ventricle. The thalamus forms the lateral walls and the fornix and corpus callosum sit above the ventricle.

Question 6Normal neuroanatomy

The dorsal root ganglion contains cell bodies of which type of neuron?

  1. Primary sensory neurons Correct answer.
  2. Preganglionic autonomic neurons
  3. Postganglionic sympathetic neurons
  4. Lower motor neurons

Explanation

Dorsal root ganglia house the pseudounipolar cell bodies of primary sensory neurons whose peripheral processes carry afferent input. Motor and autonomic neurons have their cell bodies in the cord or in autonomic ganglia.

Question 7Normal neuroanatomy

The primary visual cortex is located in which region of the cerebral hemisphere?

  1. Superior temporal gyrus
  2. Precentral gyrus of the frontal lobe
  3. Postcentral gyrus of the parietal lobe
  4. Occipital pole along the calcarine sulcus Correct answer.

Explanation

Primary visual cortex (Brodmann area 17) lies on the banks of the calcarine sulcus at the occipital pole. It receives thalamic input from the lateral geniculate nucleus.

Question 8Normal neuroanatomy

Which fiber tract connects the left and right cerebral hemispheres?

  1. Medial longitudinal fasciculus
  2. Corticospinal tract
  3. Corpus callosum Correct answer.
  4. Internal capsule

Explanation

The corpus callosum is the largest commissural bundle, carrying axons that interconnect corresponding areas of the two hemispheres. The other listed tracts are projection or association pathways.

Question 9Normal neuroanatomy

A lesion destroying the left optic nerve produces which visual field defect?

  1. Left homonymous hemianopia
  2. Total blindness of the left eye Correct answer.
  3. Right homonymous hemianopia
  4. Bitemporal hemianopia

Explanation

The optic nerve carries all fibers from one eye, so a complete lesion causes monocular blindness on that side. Chiasmal and retrochiasmal lesions produce the other patterns.

Question 10Normal neuroanatomy

The internal capsule lies between which two structures?

  1. Caudate nucleus and putamen
  2. Thalamus and hypothalamus
  3. Amygdala and hippocampus
  4. Lentiform nucleus and thalamus/caudate Correct answer.

Explanation

The internal capsule is a compact white matter band separating the lentiform nucleus laterally from the thalamus and caudate nucleus medially. Its compactness explains the dense motor deficits seen with small lacunar infarcts.

Question 11Normal neuroanatomy

Which brainstem nucleus contains the cell bodies of lower motor neurons innervating the tongue?

  1. Facial nucleus
  2. Nucleus ambiguus
  3. Oculomotor nucleus
  4. Hypoglossal nucleus Correct answer.

Explanation

The hypoglossal nucleus in the medulla gives rise to the hypoglossal nerve, which supplies the intrinsic and most extrinsic tongue muscles. The nucleus ambiguus supplies pharyngeal and laryngeal muscles.

Question 12Normal neuroanatomy

The blood supply to the posterior limb of the internal capsule is derived mainly from which artery?

  1. Anterior choroidal artery
  2. Middle cerebral artery lenticulostriate branches Correct answer.
  3. Anterior cerebral artery
  4. Posterior cerebral artery

Explanation

The lenticulostriate perforators of the middle cerebral artery supply much of the internal capsule, including the posterior limb carrying corticospinal fibers. Occlusion here produces the classic lacunar motor syndrome.

Question 13Normal neuroanatomy

Which cerebellar peduncle carries most of the output fibers from the cerebellum?

  1. Inferior cerebellar peduncle
  2. None; output is via the cerebellar cortex
  3. Middle cerebellar peduncle
  4. Superior cerebellar peduncle Correct answer.

Explanation

The superior cerebellar peduncle (brachium conjunctivum) carries the major efferent projections from the deep cerebellar nuclei to the thalamus and red nucleus. The middle and inferior peduncles are predominantly afferent.

Question 14Normal neuroanatomy

The hippocampus receives its principal input from the entorhinal cortex through which pathway?

  1. Stria terminalis
  2. Mammillothalamic tract
  3. Fornix
  4. Perforant path Correct answer.

Explanation

Entorhinal cortical axons reach the dentate gyrus and hippocampus via the perforant path, the first relay of the classic hippocampal circuit. The fornix is an output pathway from the hippocampus.

Question 15Normal neuroanatomy

Which spinal cord pathway carries fine touch and conscious proprioception from the lower limbs?

  1. Fasciculus gracilis Correct answer.
  2. Ventral spinothalamic tract
  3. Lateral spinothalamic tract
  4. Dorsal spinocerebellar tract

Explanation

The fasciculus gracilis, medial in the dorsal columns, carries fine touch and conscious proprioception from the lower limbs. The spinothalamic tracts carry pain and temperature.

Question 16Normal neuroanatomy

A lesion of the right frontal eye field would most likely produce which finding?

  1. Rightward deviation of the eyes Correct answer.
  2. Bilateral ptosis
  3. Leftward deviation of the eyes
  4. Downward deviation of the eyes

Explanation

The frontal eye field drives conjugate gaze to the contralateral side, so a destructive lesion causes the eyes to deviate toward the side of the lesion. This contrasts with pontine lesions, which deviate the eyes away from the lesion.

Question 17Normal neuroanatomy

The choroid plexus that produces CSF in the lateral ventricles is located primarily within which structure?

  1. Tela choroidea of the third ventricle
  2. Fourth ventricle roof
  3. Cerebral aqueduct
  4. Body and inferior horn of the lateral ventricle Correct answer.

Explanation

Most CSF is produced by the choroid plexus of the lateral ventricles, located in the floor of the body and in the inferior horns. The third and fourth ventricles also contain choroid plexus but contribute less volume.

Question 18Normal neuroanatomy

Which structure separates the frontal lobe from the parietal lobe on the lateral surface of the brain?

  1. Parieto-occipital sulcus
  2. Calcarine sulcus
  3. Lateral sulcus
  4. Central sulcus Correct answer.

Explanation

The central sulcus of Rolando divides the frontal lobe anteriorly from the parietal lobe posteriorly. The lateral sulcus separates the temporal lobe from the frontal and parietal opercula.

Question 19Normal neuroanatomy

The blood-brain barrier is formed primarily by which structural component?

  1. Ependymal cilia
  2. Fenestrated capillary endothelium
  3. Tight junctions between capillary endothelial cells Correct answer.
  4. Perivascular macrophages

Explanation

Tight junctions between nonfenestrated endothelial cells of CNS capillaries form the core of the blood-brain barrier, supported by astrocytic endfeet and pericytes. Fenestrated endothelium occurs in circumventricular organs where the barrier is absent.

Question 20Normal neuroanatomy

The basilar artery is formed by the union of which vessels?

  1. Two internal carotid arteries
  2. Two posterior cerebral arteries
  3. Two vertebral arteries Correct answer.
  4. Internal carotid and vertebral arteries

Explanation

The two vertebral arteries join at the lower border of the pons to form the midline basilar artery. The basilar artery then bifurcates into the posterior cerebral arteries.

Question 21Normal neuroanatomy

The thalamus projects to the cerebral cortex mainly through which structure?

  1. Anterior commissure
  2. Cingulum
  3. Internal medullary lamina
  4. Corona radiata Correct answer.

Explanation

Thalamocortical fibers fan out through the corona radiata as they ascend toward the cortex. The internal medullary lamina divides thalamic nuclei but is not the projection route.

Question 22Normal neuroanatomy

The Edinger-Westphal nucleus provides parasympathetic preganglionic fibers to which ganglion?

  1. Otic ganglion
  2. Submandibular ganglion
  3. Pterygopalatine ganglion
  4. Ciliary ganglion Correct answer.

Explanation

Preganglionic parasympathetic fibers from the Edinger-Westphal nucleus travel with the oculomotor nerve to the ciliary ganglion, whose postganglionic fibers constrict the pupil and accommodate the lens. The other ganglia supply salivary and lacrimal targets.

Question 23Normal neuroanatomy

A lesion of the medial longitudinal fasciculus on the right side would most likely produce which finding on attempted leftward gaze?

  1. Failure of the right eye to adduct
  2. Failure of the left eye to adduct Correct answer.
  3. Bilateral failure of adduction
  4. Failure of the right eye to abduct

Explanation

The MLF carries internuclear fibers from the contralateral abducens nucleus to the ipsilateral medial rectus subnucleus. A right MLF lesion interrupts signals to the right oculomotor nucleus, so the left eye fails to adduct on leftward gaze (internuclear ophthalmoplegia).

Question 24Normal neuroanatomy

The artery most commonly implicated in infarction of the medial medulla is a branch of which vessel?

  1. Superior cerebellar artery
  2. Posterior cerebral artery
  3. Posterior inferior cerebellar artery
  4. Anterior spinal artery Correct answer.

Explanation

Medial medullary branches arise from the anterior spinal artery and its vertebral contributions, supplying the pyramid, medial lemniscus, and hypoglossal nucleus. Lateral medullary infarction instead reflects posterior inferior cerebellar artery occlusion.

Question 25Normal neuroanatomy

The deep cerebellar nuclei receive their principal inhibitory input from which cells?

  1. Purkinje cells Correct answer.
  2. Mossy fibers
  3. Granule cells
  4. Climbing fibers

Explanation

Purkinje cells are the sole output of the cerebellar cortex and project inhibitory GABAergic fibers to the deep nuclei. Climbing and mossy fibers are excitatory afferents, and granule cells are excitatory interneurons.

Question 26Normal neuroanatomy

Which cell type forms the myelin sheath around axons in the central nervous system?

  1. Astrocyte
  2. Oligodendrocyte Correct answer.
  3. Microglial cell
  4. Schwann cell

Explanation

Oligodendrocytes extend multiple processes that wrap around axons in the CNS to form myelin. Schwann cells perform this role in the peripheral nervous system, while astrocytes and microglia have other functions.

Question 27Normal neuroanatomy

The cell bodies of upper motor neurons that project via the corticospinal tract are located primarily in which cortical layer?

  1. Layer VI
  2. Layer V Correct answer.
  3. Layer IV
  4. Layer III

Explanation

Large pyramidal cells in layer V of the motor cortex give rise to the corticospinal and corticobulbar tracts. Layer III contains corticocortical projection neurons, layer IV is the main thalamic input layer, and layer VI projects back to the thalamus.

Question 28Normal neuroanatomy

The cell bodies of primary sensory neurons that convey discriminative touch from the face are located in which ganglion?

  1. Trigeminal ganglion Correct answer.
  2. Nodose ganglion
  3. Superior cervical ganglion
  4. Geniculate ganglion

Explanation

The trigeminal ganglion contains the pseudounipolar cell bodies of primary afferents for the trigeminal nerve, including those mediating fine touch from the face. The geniculate ganglion belongs to the facial nerve, the nodose ganglion to the vagus, and the superior cervical ganglion is autonomic.

Question 29Normal neuroanatomy

Which structure forms the floor of the fourth ventricle?

  1. Rhomboid fossa Correct answer.
  2. Superior medullary velum
  3. Inferior medullary velum
  4. Tela choroidea

Explanation

The rhomboid fossa is the diamond-shaped floor of the fourth ventricle, formed by the dorsal surfaces of the pons and medulla. The superior and inferior medullary vela form parts of the roof, and the tela choroidea contributes to the roof as well.

Question 30Normal neuroanatomy

The cell bodies of dopaminergic neurons that project to the striatum and degenerate in Parkinson disease are located in which structure?

  1. Locus coeruleus
  2. Globus pallidus internus
  3. Substantia nigra pars reticulata
  4. Substantia nigra pars compacta Correct answer.

Explanation

Dopaminergic neurons of the substantia nigra pars compacta project to the striatum and are lost in Parkinson disease. The pars reticulata is a GABAergic output nucleus, the globus pallidus internus is also a GABAergic output, and the locus coeruleus is noradrenergic.

Question 31Normal neuroanatomy

Which cranial nerve carries preganglionic parasympathetic fibers that synapse in the ciliary ganglion?

  1. Vagus nerve
  2. Facial nerve
  3. Oculomotor nerve Correct answer.
  4. Glossopharyngeal nerve

Explanation

Preganglionic parasympathetic fibers from the Edinger-Westphal nucleus travel in the oculomotor nerve to synapse in the ciliary ganglion. The facial, glossopharyngeal, and vagus nerves carry parasympathetic fibers to other ganglia.

Question 32Normal neuroanatomy

The cell bodies of second-order neurons in the dorsal column–medial lemniscus pathway are located in which structure?

  1. Postcentral gyrus
  2. Nucleus cuneatus and nucleus gracilis Correct answer.
  3. Dorsal root ganglion
  4. Ventral posterolateral nucleus of the thalamus

Explanation

Primary afferents ascend in the dorsal columns and synapse on second-order neurons in the nucleus gracilis and nucleus cuneatus of the medulla. These neurons decussate and ascend as the medial lemniscus to the thalamus, where third-order neurons reside.

Question 33Normal neuroanatomy

The cell bodies of lower motor neurons that innervate skeletal muscle of the limbs are located in which spinal cord region?

  1. Posterior funiculus
  2. Ventral horn Correct answer.
  3. Lateral horn
  4. Dorsal horn

Explanation

Lower motor neurons are located in the ventral horn of the spinal cord gray matter and send their axons out through the ventral roots. The dorsal horn processes sensory input, the lateral horn contains autonomic neurons, and the posterior funiculus contains ascending sensory tracts.

Question 34Normal neuroanatomy

A lesion of the left optic tract would most likely produce which visual field defect?

  1. Right homonymous hemianopia Correct answer.
  2. Left monocular blindness
  3. Bitemporal hemianopia
  4. Left homonymous hemianopia

Explanation

The left optic tract carries fibers from the temporal retina of the left eye and the nasal retina of the right eye, which subserve the right visual field. Therefore, a left optic tract lesion causes a right homonymous hemianopia.

Question 35Normal neuroanatomy

The cell bodies of neurons that give rise to the fornix are located in which structure?

  1. Amygdala
  2. Hippocampus Correct answer.
  3. Septal nucleus
  4. Mammillary body

Explanation

The fornix is the major efferent tract of the hippocampus, carrying axons from pyramidal cells of the subiculum and hippocampus. The amygdala, mammillary body, and septal nuclei are targets or related structures but are not the principal source of fornical fibers.

Question 36Normal neuroanatomy

A lesion of the left lateral geniculate nucleus would most likely produce which visual field defect?

  1. Right monocular blindness
  2. Right homonymous hemianopia Correct answer.
  3. Left superior quadrantanopia
  4. Binasal hemianopia

Explanation

The lateral geniculate nucleus receives fibers from the contralateral visual field via the optic tract. A left lateral geniculate lesion therefore produces a right homonymous hemianopia, similar to a left optic tract lesion.

Question 37Normal neuroanatomy

Which brainstem nucleus contains the cell bodies of lower motor neurons that innervate the muscles of mastication?

  1. Hypoglossal nucleus
  2. Facial motor nucleus
  3. Ambiguus nucleus
  4. Trigeminal motor nucleus Correct answer.

Explanation

The trigeminal motor nucleus in the pons supplies the muscles of mastication through the mandibular division of the trigeminal nerve. The facial, hypoglossal, and ambiguus nuclei innervate facial expression, tongue, and pharyngeal/laryngeal muscles, respectively.

Question 38Normal neuroanatomy

The cell bodies of neurons that provide the major cholinergic input to the cerebral cortex are located in which structure?

  1. Locus coeruleus
  2. Substantia nigra
  3. Raphe nuclei
  4. Nucleus basalis of Meynert Correct answer.

Explanation

The nucleus basalis of Meynert in the basal forebrain is the main source of cholinergic projections to the cerebral cortex and is affected in Alzheimer disease. The substantia nigra is dopaminergic, the raphe nuclei are serotonergic, and the locus coeruleus is noradrenergic.

Question 39Normal neuroanatomy

The cell bodies of neurons that give rise to the middle cerebellar peduncle are located in which structure?

  1. Vestibular nuclei
  2. Dentate nucleus
  3. Pontine nuclei Correct answer.
  4. Inferior olive

Explanation

The middle cerebellar peduncle consists of axons from the contralateral pontine nuclei, which relay corticopontine fibers to the cerebellum. The inferior olive projects via the inferior cerebellar peduncle, the dentate nucleus projects via the superior cerebellar peduncle, and the vestibular nuclei project via the inferior cerebellar peduncle.

Question 40Normal neuroanatomy

The cell bodies of neurons that provide the major noradrenergic innervation of the cerebral cortex are located in which structure?

  1. Raphe nuclei
  2. Substantia nigra
  3. Nucleus basalis of Meynert
  4. Locus coeruleus Correct answer.

Explanation

The locus coeruleus in the pons is the principal source of noradrenergic projections to the cerebral cortex and many other forebrain regions. The raphe nuclei are serotonergic, the nucleus basalis of Meynert is cholinergic, and the substantia nigra is dopaminergic.

Question 41Diagnostic neuropathology and patient care consultation

A 62-year-old man dies with a clinical diagnosis of sporadic Creutzfeldt-Jakob disease. Which microscopic finding is most characteristic of this disorder?

  1. Eosinophilic Lewy bodies in substantia nigra neurons
  2. Neurofibrillary tangles in a flame-shaped distribution
  3. Spongiform change with neuronal loss and astrogliosis Correct answer.
  4. Demyelinating plaques with perivascular lymphocytes

Explanation

Sporadic CJD is a prion disease whose hallmark is vacuolation of the neuropil (spongiform change) accompanied by neuronal loss and reactive astrogliosis. Tangles, Lewy bodies, and demyelinating plaques define other disease classes.

Question 42Diagnostic neuropathology and patient care consultation

A pathologist examines a brain biopsy showing a highly cellular tumor with pseudopalisading necrosis and microvascular proliferation. Which diagnosis is most consistent with these features?

  1. Pilocytic astrocytoma
  2. Meningioma
  3. Ependymoma
  4. Glioblastoma Correct answer.

Explanation

Pseudopalisading necrosis and microvascular proliferation are defining histologic features of glioblastoma, an IDH-wildtype diffuse astrocytic tumor. Pilocytic astrocytomas are low grade, ependymomas form rosettes and perivascular pseudorosettes, and meningiomas are extra-axial.

Question 43Diagnostic neuropathology and patient care consultation

A 70-year-old woman has progressive memory loss; autopsy shows abundant neuritic plaques and neurofibrillary tangles in the hippocampus and neocortex. Which protein forms the core of the neuritic plaques?

  1. Alpha-synuclein
  2. Tau
  3. TDP-43
  4. Amyloid beta Correct answer.

Explanation

Neuritic plaques contain an extracellular core of amyloid beta peptide derived from amyloid precursor protein. Tau forms the paired helical filaments of tangles, alpha-synuclein forms Lewy bodies, and TDP-43 is seen in frontotemporal lobar degeneration and ALS.

Question 44Diagnostic neuropathology and patient care consultation

A newborn with a lumbosacral skin dimple and tuft of hair is evaluated. Which spinal malformation should be suspected?

  1. Tethered cord with spinal dysraphism Correct answer.
  2. Amyotrophic lateral sclerosis
  3. Syringomyelia
  4. Spinal muscular atrophy

Explanation

Cutaneous stigmata over the lumbosacral region, such as a hair tuft, dimple, or lipoma, raise concern for occult spinal dysraphism with a tethered cord. These findings warrant imaging to prevent progressive neurologic deficit.

Question 45Diagnostic neuropathology and patient care consultation

A 55-year-old man has a brain abscess. Which histologic feature best distinguishes an abscess cavity from a necrotic glioblastoma?

  1. Surrounding edema
  2. A well-formed collagenous capsule with a三层 fibrous wall Correct answer.
  3. Presence of macrophages
  4. Central necrosis

Explanation

A brain abscess typically has a三层 organized wall with a collagenous capsule, granulation tissue, and a fibrotic rim, which reflects its infectious and reactive nature. Glioblastoma shows infiltrative tumor cells with pseudopalisading necrosis and lacks a true collagenous capsule.

Question 46Diagnostic neuropathology and patient care consultation

A 3-year-old child has a posterior fossa mass with uniform small round blue cells, Homer Wright rosettes, and frequent mitoses. Which tumor is most likely?

  1. Medulloblastoma Correct answer.
  2. Choroid plexus papilloma
  3. Atypical teratoid/rhabdoid tumor
  4. Pilocytic astrocytoma

Explanation

Medulloblastoma is an embryonal tumor of the cerebellum composed of small round blue cells with Homer Wright rosettes and high mitotic activity. AT/RT shows rhabdoid cells and INI1 loss, pilocytic astrocytoma is low grade, and choroid plexus papilloma forms papillary structures.

Question 47Diagnostic neuropathology and patient care consultation

A 45-year-old woman has a dural-based extra-axial mass with whorls of meningothelial cells and psammoma bodies. Which feature most strongly predicts a higher WHO grade?

  1. Nests of uniform cells
  2. Prominent whorl formation
  3. Presence of psammoma bodies
  4. Brain invasion with increased mitotic rate Correct answer.

Explanation

Meningioma grading depends on mitotic activity, brain invasion, and specific histologic patterns; brain invasion and elevated mitotic index raise the grade. Psammoma bodies, uniform nests, and whorls are typical of grade 1 meningioma.

Question 48Diagnostic neuropathology and patient care consultation

A 30-year-old man has a cystic lesion in the lateral ventricle with a mural nodule composed of clear cells and prominent vasculature. Which diagnosis is favored?

  1. Hemangioblastoma Correct answer.
  2. Subependymoma
  3. Central neurocytoma
  4. Oligodendroglioma

Explanation

Hemangioblastoma is a cystic tumor with a mural nodule of vacuolated stromal cells and a rich capillary network, often in the cerebellum but also periventricular. Central neurocytoma is calcified and intraventricular, subependymoma is hypocellular, and oligodendroglioma shows fried-egg cells with 1p/19q codeletion.

Question 49Diagnostic neuropathology and patient care consultation

A patient with a frontal lobe mass undergoes resection; histology shows a diffuse astrocytoma. Which molecular finding defines IDH-mutant astrocytoma?

  1. H3 K27M mutation
  2. 1p/19q codeletion
  3. IDH1 or IDH2 mutation Correct answer.
  4. MGMT promoter methylation

Explanation

IDH1 or IDH2 mutations define IDH-mutant diffuse astrocytomas and are a key diagnostic and prognostic marker. 1p/19q codeletion defines oligodendroglioma, H3 K27M defines diffuse midline glioma, and MGMT methylation is a predictive marker rather than a diagnostic definition.

Question 50Diagnostic neuropathology and patient care consultation

A 65-year-old man has a peripheral nerve biopsy showing a granulomatous inflammation with acid-fast bacilli. Which organism is most likely?

  1. Mycobacterium leprae Correct answer.
  2. Candida albicans
  3. Borrelia burgdorferi
  4. Neisseria meningitidis

Explanation

Leprosy caused by Mycobacterium leprae produces granulomatous inflammation of peripheral nerves with acid-fast bacilli. Meningococcus causes meningitis, Borrelia causes Lyme neuroborreliosis, and Candida causes fungal infection.